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What is pharmacodynamics?
The study of how drugs affect the body.
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What factors affect drug action?
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Define potency in pharmacodynamics.
The amount of drug needed to produce a desired effect.
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What is efficacy in drug action?
The maximum effect a drug can produce.
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How do agonists work?
They activate receptors to produce a biological response.
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What role do antagonists play?
They block receptors and prevent a biological response.
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What is the therapeutic index?
The ratio between the toxic dose and effective dose of a drug.
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Define bioavailability.
The proportion of a drug that enters circulation when introduced into the body.
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What does half-life measure?
The time it takes for the concentration of a drug to reduce to half its initial value.
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What is dose-response relationship?
The relationship between the dose of a drug and the magnitude of its pharmacological effect.
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What can tolerance lead to in pharmacotherapy?
Reduced response to a drug after repeated use.
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What is the significance of receptor phosphorylation?
It can alter receptor activity and signaling potency.
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What are enzyme inhibitors?
Substances that decrease enzyme activity, affecting drug metabolism.
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What effect do enzyme inducers have?
They increase enzyme activity, leading to faster drug metabolism.
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What is the importance of clinical trials in pharmacodynamics?
They help evaluate the safety and efficacy of drug therapies.
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Identify a key aspect of patient variability in drug response.
Genetic differences can affect drug metabolism and action.
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What is the impact of age on pharmacodynamics?
Age affects drug absorption, distribution, metabolism, and excretion.
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How can drug interactions alter therapeutic effects?
They can either enhance or diminish drug actions and side effects.
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Define agonist-antagonist activity.
Drugs that activate some receptors while blocking others.
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What is maximal efficacy?
The greatest intensity of effect that a drug can produce.
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Explain the concept of selectivity in pharmacodynamics.
The ability of a drug to preferentially elicit responses from one receptor subtype over others.
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What is the study of what the drug does to the body called?
Pharmacodynamics
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What does pharmacokinetics study?
What the body does to the drug.
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What processes are included in pharmacokinetics?
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What are the four major questions pharmacodynamics answers?
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What does 'action' refer to in pharmacodynamics?
The initial combination of the drug with its target molecule.
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What does 'effect' refer to in pharmacodynamics?
The measurable change in physiological function from the drug's action.
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What is the action of Captopril?
Inhibits angiotensin-converting enzyme (ACE).
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What is the effect of Captopril?
Vasodilation, leading to a fall in blood pressure.
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Why is it important to understand drug action?
Different drugs can produce the same effect via different mechanisms.
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What is the common mechanism of drug action?
Inhibition of enzymes.
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What are the main targets of drug action?
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How can a drug alter biochemical reaction rates?
By modulating enzyme activity.
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What types of proteins do most drugs target?
Functional proteins.
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What are structural proteins?
Proteins that form the body's framework, e.g., collagen.
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What happens when enzymes are inhibited by drugs?
The rate of biochemical reactions is altered.
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Is stimulation of enzymes common in drug action?
No, it is rare.
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What is competitive inhibition?
It's when an inhibitor competes with the substrate for the active site. Can be reversible or irreversible.
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What types can competitive inhibition be?
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What is noncompetitive inhibition?
It's when an inhibitor binds to an enzyme, reducing its activity regardless of the substrate concentration.
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What is the function of an enzyme?
Enzymes act as catalysts to accelerate biochemical reactions.
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What is an enzyme's catalytic site?
It's the active site where the substrate binds to undergo a reaction, similar to the blades of scissors.
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What happens when a substrate binds to an enzyme?
The substrate undergoes a biochemical reaction to form a product.
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What is the role of inhibitors in enzyme activity?
Inhibitors decrease enzyme activity by blocking the active site or altering enzyme shape.
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How does reversible inhibition differ from irreversible inhibition?
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What is one characteristic of a competitive inhibitor?
It structurally resembles the substrate and binds to the active site of the enzyme.
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What is an example of an enzyme action?
An enzyme converting a substrate like glucose into glucose-6-phosphate.
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What does enzyme velocity depend on?
The number of active enzyme molecules.
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What is the Michaelis constant (kM)?
Substrate concentration at which half of the enzyme molecules are active.
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What does Vmax represent?
Maximum rate of the enzyme-catalyzed reaction when fully saturated with substrate.
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What happens at low substrate concentration?
Few enzymes are active.
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What is competitive inhibition?
Inhibition where a drug resembles the substrate and competes for the same catalytic site.
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Effect of competitive inhibition on kM?
kM increases because more substrate is needed for half-maximal enzyme activity.
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What is reversible competitive inhibition?
Inhibitor binds weakly and can be displaced by substrate, Vmax remains unchanged.
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Example of reversible competitive inhibitor?
Physostigmine inhibits cholinesterase and can be overcome by increasing acetylcholine.
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What is irreversible competitive inhibition?
Inhibitor binds strongly and forms a covalent bond, cannot be displaced by substrate.
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Effect of irreversible competitive inhibition on Vmax?
Vmax decreases because fewer active enzyme molecules are available.
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Example of an irreversible competitive inhibitor?
Organophosphate compounds inhibit cholinesterase irreversibly.
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What is noncompetitive inhibition?
Inhibitor binds to a different site on the enzyme, causing structural changes and Vmax decreases.
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Effect of noncompetitive inhibition on kM?
kM remains unchanged.
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Example of a noncompetitive inhibitor?
Aspirin inhibits cyclooxygenase (COX) noncompetitively.
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Summary of reversible competitive inhibition?
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Summary of irreversible competitive inhibition?
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Summary of noncompetitive inhibition?
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What do transport proteins do?
Control the movement of ions and molecules across biological membranes.
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What are the main types of transport proteins?
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What is the role of ion pumps?
Move ions against concentration gradients using ATP.
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What is an example of an ion pump?
Na+/K+-ATPase pump – Maintains sodium and potassium balance.
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What do carrier proteins do?
Utilize ion gradients created by pumps to transport substances.
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Give an example of a carrier protein.
Na+/Cl- cotransporter in the renal tubules.
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What function do ion channels serve?
Allow passive movement of ions down their electrochemical gradient.
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How do drugs affect transport proteins?
They can inhibit or stimulate their activity.
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What is the effect of digoxin on Na+/K+-ATPase?
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What drug inhibits noradrenaline reuptake?
Cocaine - Blocks noradrenaline transporter (NET).
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What do thiazide diuretics inhibit?
Inhibit Na+/Cl- cotransporter in the distal convoluted tubule.
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What is the effect of omeprazole?
Inhibits H+/K+-ATPase enzyme, reducing gastric acidity.
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How do SSRIs work?
Block serotonin reuptake, enhancing serotonergic transmission.
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What is one mechanism of drug action related to receptors?
Modulating the activity of specialized macromolecules, usually proteins.
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What does a receptor bind?
A drug or endogenous chemical messenger (e.g., hormone, neurotransmitter)
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What is the function of receptors?
To recognize drug molecules and transduce their signals into biological effects
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What happens when a drug binds to a receptor?
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What is an agonist?
A substance that activates a receptor
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What is an antagonist?
A substance that blocks a receptor
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What type of response do receptors initiate?
A cellular response
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What are endogenous chemical messengers?
Substances like hormones and neurotransmitters produced within the body
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What is the role of a drug in receptor interactions?
To modulate biological effects by binding to receptors
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Can drugs act as both agonists and antagonists?
Yes, based on their interaction with specific receptors
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What determines the effect of a drug on a receptor?
Whether it acts as an agonist or antagonist
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What is an agonist?
A substance that binds to a receptor and activates it, producing a biological response.
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What is an antagonist?
A substance that binds to a receptor but does not activate it, preventing the action of an agonist.
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What do agonists mimic?
The effect of endogenous substances.
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What do antagonists block?
The effects of agonists.
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What are ligand-gated ion channels?
Integral membrane proteins that form ion channels, opening upon agonist binding.
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What happens when an agonist binds to ligand-gated ion channels?
The channel opens, allowing ions to cross the membrane.
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Give an example of a ligand-gated ion channel.
Nicotinic acetylcholine receptor (nAChR).
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What is the effect of acetylcholine binding to nAChR?
Opens the channel, allowing sodium in and potassium out, leading to muscle contraction.
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What is an example of an agonist for nAChR?
Nicotine.
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What is an example of an antagonist for nAChR?
Tubocurarine (causes muscle relaxation).
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What are G-protein-coupled receptors?
Receptors coupled to intracellular G-proteins that modulate enzymes or ion channels.
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What is the mechanism of G-protein-coupled receptors?
Agonist binds, activating G-protein, which modulates effectors.
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What are the key second messengers involved in G-protein signaling?
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Give an example of a G-protein-coupled receptor.
Beta-adrenergic receptor, activated by adrenaline.
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What does the binding of adrenaline to beta receptors do?
Stimulates adenylate cyclase, increasing cAMP levels.
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What are enzyme-linked receptors?
Transmembrane proteins with intrinsic enzymatic activity, activating upon ligand binding.
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What type of receptor is the insulin receptor?
A tyrosine kinase receptor.
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What happens when insulin binds to its receptor?
Activates tyrosine kinase, leading to phosphorylation of intracellular proteins.
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Give a drug example that acts as an agonist at insulin receptors.
Recombinant human insulin.
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What are intracellular receptors?
Receptors located in the cytoplasm or nucleus that bind lipid-soluble substances.
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How do intracellular receptors affect cellular function?
By interacting with DNA to regulate gene transcription.
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What kind of ligands activate intracellular receptors?
Lipid-soluble substances.
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Give an example of an intracellular receptor ligand.
Steroid hormones like glucocorticoids.
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What action does prednisolone have?
Acts on intracellular glucocorticoid receptors to suppress inflammation.
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What does levothyroxine regulate?
Metabolism by acting on nuclear thyroid hormone receptors.
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What is the response time for G-protein-coupled receptors?
Intermediate response (seconds), involving second messengers.
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What defines enzyme-linked receptors?
Slow response (minutes to hours), mediated by phosphorylation cascades.
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What is the response time for intracellular receptors?
Very slow response (hours to days).
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What is the main function of ligand-gated ion channels?
Mediates ion fluxes for fast signaling.
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What role do G-protein-coupled receptors play in signaling?
Involve second messengers for cellular responses.
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How do enzyme-linked receptors facilitate cellular responses?
Through phosphorylation cascades over minutes to hours.
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What type of response do intracellular receptors provide?
Provides very slow responses over hours to days.
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What is a Full Agonist?
Produces the maximum possible response by fully activating receptors.
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What is a Partial Agonist?
Binds to receptors but produces a submaximal response even at full occupancy.
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How does a Partial Agonist act?
Can act as both an agonist and an antagonist depending on context.
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What is an Inverse Agonist?
Binds to the same receptor as an agonist but induces an opposite response.
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What is the function of an Antagonist?
Binds to the receptor without activating it, preventing agonist binding.
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What are the two types of Antagonists?
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How does Adrenaline function as a drug?
Acts as an agonist on beta receptors to increase heart rate.
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What is the role of Propranolol?
Acts as a beta receptor antagonist to decrease heart rate and blood pressure.
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How does Diazepam affect neurotransmission?
Enhances GABA receptor activity, increasing chloride ion influx and causing sedation.
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What effect does Atropine have on the body?
Blocks muscarinic receptors, reducing secretions and dilating pupils.
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What does Prednisolone activate?
Activates intracellular glucocorticoid receptors to produce anti-inflammatory effects.
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What is the dose-response relationship?
It is the relationship between the dose of a drug and the magnitude of its effect.
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What does the dose-response relationship help determine?
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What are the two types of dose-response relationships?
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Explain the graded dose-response relationship.
Response measured continuously; increases with dose (e.g. blood pressure response).
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What happens in the linear region of the sigmoid curve?
Small dose increases result in large response increases.
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What occurs in the plateau region of the dose-response curve?
Response reaches maximum (Emax); further increases won't enhance effect.
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Define Emax.
The greatest effect produced by the drug regardless of dose.
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What is EC50?
Concentration producing 50% of maximum response; indicates potency.
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What does a steep slope indicate on the dose-response curve?
Small dose changes lead to large effect changes.
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Differentiate between efficacy and potency.
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What is the receptor occupancy theory?
Response is proportional to the fraction of receptors occupied.
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Describe the quantal dose-response relationship.
All-or-none response representing percentage of a population showing effect.
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Example of a quantal response?
Percentage of subjects falling asleep with varying sedative doses.
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Graphing which relationship uses a logarithmic scale?
Both graded and quantal dose-response relationships.
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What shape does the curve take when drug sensitivity data is plotted?
A sigmoid (S-shaped) curve.
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What does the y-axis represent when plotting drug sensitivity data?
The distribution of sensitivity to the drug.
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What type of curve is obtained when data is plotted?
A frequency distribution curve.
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What does a sigmoid curve indicate in drug sensitivity studies?
Intermediate sensitivity levels among subjects.
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What is ED50?
The dose producing the desired effect in 50% of the population.
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What does TD50 represent?
The dose producing a toxic effect in 50% of the population.
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What is the definition of LD50?
The dose causing death in 50% of experimental animals.
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What is the Therapeutic Index (TI)?
The ratio of TD50 to ED50; indicates drug safety.
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What does a high TI indicate?
The drug is relatively safe; toxic dose is much higher than effective dose.
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What does a low TI signify?
The drug is potentially dangerous; effective and toxic doses are close.
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Which drug has a high TI?
Penicillin; considered very safe.
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Which drugs have low TIs?
Digoxin, lithium, warfarin; require close monitoring.
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What is the therapeutic window?
The range between minimum effective concentration (MEC) and minimum toxic concentration (MTC).
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What defines narrow therapeutic windows?
Require frequent plasma level monitoring to avoid toxicity.
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How does body weight affect drug dosage?
Doses are calculated per kilogram; larger mass = higher doses.
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How do lipophilic drugs distribute in obese individuals?
They accumulate in adipose tissue, causing prolonged effects.
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What are the drug metabolism effects in newborns?
Reduced liver and kidney function; careful dose adjustments needed.
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What syndrome can chloramphenicol cause in infants?
Gray baby syndrome; due to immature metabolism.
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What age-related change affects the elderly?
Reduced renal clearance and liver metabolism; sensitivity to drugs increases.
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How do hormonal differences affect drug metabolism in sexes?
Women may metabolize drugs (e.g., alcohol) slower.
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How does pregnancy impact pharmacokinetics?
Increased plasma volume, renal clearance, and protein binding changes.
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What toxicity can occur in cats with certain drugs?
Inability to metabolize paracetamol efficiently; leads to toxicity.
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How do genetic factors alter drug response?
Variations in enzymes and receptors can significantly influence outcomes.
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What is an example of a pharmacogenetic variation?
Slow and fast acetylators affect isoniazid metabolism.
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How can G6PD deficiency affect drug use?
Increases risk of hemolysis with certain drugs like primaquine.
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What can happen when increasing doses of a medication are required?
May require increasing doses to maintain the same effect.
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Name examples of medications that may require increasing doses.
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What is tachyphylaxis?
A rapid decrease in drug response after a few doses in quick succession.
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Give examples of drugs that show tachyphylaxis.
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What causes tachyphylaxis in ephedrine and tyramine?
Depletion of stored noradrenaline.
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What occurs in drug interactions?
When two or more drugs affect each other's action.
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What are pharmacodynamic interactions?
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What are pharmacokinetic interactions?
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How does aspirin influence the effect of warfarin?
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What effect does rifampicin have on oral contraceptives?
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What effect does erythromycin have on theophylline?
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What environmental factors can modify drug action?
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How does high environmental temperature affect drug action?
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What is the placebo effect?
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Which substances can affect enzyme induction?
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How can psychological factors influence drug responses?
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What is drug antagonism?
A phenomenon where the effect of one drug is inhibited by another drug.
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What is synergism?
When two drugs enhance each other's effects.
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When can antagonism be beneficial?
To counteract poisoning or overdose (e.g., naloxone with morphine).
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When can antagonism be harmful?
When an essential therapeutic effect is blocked (e.g., beta-blockers with beta-agonists).
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What are the types of drug antagonism?
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What is physical antagonism?
When two drugs physically oppose each other's actions without chemical reaction.
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Give an example of physical antagonism.
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What is chemical antagonism?
When two substances chemically react to form an inactive product.
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Give an example of chemical antagonism.
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What is physiological antagonism?
When drugs act on different receptors but produce opposite effects.
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Give an example of physiological antagonism.
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What is pharmacological antagonism?
Occurs when two drugs act on the same receptor system; antagonists block agonists.
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What is competitive antagonism?
Antagonist competes with agonist for the same receptor site, reversible binding.
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What results from competitive antagonism?
Maximum response remains the same; EC50 increases with higher agonist doses.
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What is the difference between competitive and non-competitive antagonism?
Competitive antagonism is reversible; non-competitive cannot be overcome by increasing agonist concentration.
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What effect does a 50% increase in dose have on the dose-response curve?
Shifts to the right.
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What does atropine do at muscarinic receptors?
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What is the effect of propranolol at β-adrenergic receptors?
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How does mepyramine affect H1-receptors?
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What characterizes irreversible antagonism?
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What binds irreversibly to receptors?
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What happens to Emax in irreversible binding?
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What happens to EC50 in irreversible binding?
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What is an example of an irreversible antagonist?
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What characterizes non-competitive antagonism?
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What is the result of non-competitive antagonism?
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What is an example of a non-competitive antagonist?
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What is a partial agonist?
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What happens when a partial agonist is administered with a full agonist?
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What is an example of a partial agonist?
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What is an inverse agonist?
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What do inverse agonists stabilize?
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What are examples of inverse agonists?
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What is drug synergism?
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What is additive synergism?
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What is supra-additive synergism?
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What is a clinical use of antagonism?
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What are beta-blockers used for?
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What is the significance of understanding antagonism?
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What types of mechanisms can lead to antagonism?
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What produces effects by binding to receptors?
Drugs
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What does affinity refer to?
The ability of a drug to bind to its receptor
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What is potency a measure of?
How much drug is required to produce a given effect
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What does efficacy determine?
The maximum effect (Emax) a drug can produce
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What type of agonist has both high affinity and high efficacy?
Full agonist
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Which agonist produces a submaximal response?
Partial agonist
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What is an example of a full agonist?
Morphine
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What does an antagonist do?
Binds to the receptor without activating it and blocks agonist actions
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What is the main premise of Occupation Theory?
The response is directly proportional to the number of receptors occupied
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What does Rate Theory emphasize?
The rate of drug-receptor interaction
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What happens when all receptors are occupied according to Occupation Theory?
Maximum effect (Emax) occurs
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What are the limitations of Occupation Theory?
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What happens with drugs that associate and dissociate rapidly?
Produce stronger effects
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What is an example of an inverse agonist?
Propranolol
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How does a partial agonist act in the presence of a full agonist?
Can act as an antagonist
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What is the term for the concentration producing 50% of maximum response?
EC50
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What type of receptor activity do inverse agonists target?
Constitutive activity
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What does high affinity enable for a drug?
Bind tightly even at low concentrations
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Which phenomenon cannot be explained by Rate Theory?
Long-lasting effects of irreversible binding drugs
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What are the two states of receptors according to modern receptor theory?
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Can receptors exist in the active state without a ligand?
Yes, a small fraction of receptors may spontaneously exist in the active state even without a ligand.
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What does 'R' represent in receptor theory?
R represents the inactive state of a receptor.
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What does 'R*' represent in receptor theory?
R* represents the active state of a receptor.
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What is the significance of interconvertible states of receptors?
It allows receptors to switch between inactive and active states, affecting signaling.
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What concept is highlighted by spontaneous receptor activation?
It highlights the dynamic nature and efficiency of receptor signaling.
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What shifts equilibrium toward activation in receptors?
Agonists have higher affinity for R*.
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What stabilizes the inactive state of a receptor?
Inverse agonists have higher affinity for R.
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What is the effect of neutral antagonists?
They have equal affinity for R and R* and block both activities.
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What concept explains constitutive receptor activity?
Constitutive activity occurs with drug interactions that affect receptor states.
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What defines spare receptors?
A receptor system has spare receptors when Emax is achieved without occupying all receptors.
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How does spare receptor concept relate to cardiac muscle?
Maximal response to adrenaline can occur with only partial occupancy of ẞ1-receptors.
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What is the impact of irreversible antagonists in relation to spare receptors?
Emax may not decrease until receptor reserve is exhausted.
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What influences receptor number and sensitivity?
They can be upregulated or downregulated by various influences.
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What leads to upregulation of receptors?
Prolonged exposure to antagonists or deficiency of agonist.
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What is an example of upregulation effects?
Chronic ẞ-blocker use may cause rebound tachycardia upon withdrawal.
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What causes downregulation of receptors?
Prolonged exposure to agonists results in downregulation.
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What is receptor-effector coupling?
It describes the relationship between receptor activation and cellular response.
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How does coupling efficiency affect drug response?
Efficiently coupled drugs produce strong effects with limited activation.
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What is the cyclic AMP (cAMP) pathway?
Activated by ẞ1- and ẞ2-adrenergic receptors, increases cAMP and activates PKA.
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What is the role of protein kinase A (PKA)?
PKA phosphorylates target proteins leading to various physiological effects.
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What triggers the phosphatidylinositol pathway?
Gq-protein-coupled receptors lead to formation of IP3 and DAG.
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What does DAG cause in cells?
DAG leads to Ca²+ release and activation of protein kinase C (PKC).
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What is the role of nitric oxide (NO) in signaling?
NO activates the cyclic GMP pathway, mediating smooth muscle relaxation.
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How is ion channel modulation achieved?
Ligand-gated channels open/close upon ligand binding, affecting membrane potential.
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What describes pharmacodynamics?
Pharmacodynamics involves how drugs act on the body, including efficacy and receptor interactions.
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What is the difference between action and effect in pharmacology?
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What are the types of membrane receptors?
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What differentiates agonists from antagonists?
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What do dose-response relationships define?
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What does potency refer to?
The amount of drug needed to produce an effect.
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What is efficacy in pharmacology?
The maximum effect a drug can produce.
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What does therapeutic index (TI) indicate?
The safety margin of a drug; a ratio comparing the effective dose to the toxic dose.
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What factors modify drug action?
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What types of antagonism exist?
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What are the theories of drug action?
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What does binding translate into?
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What forms the foundation for rational pharmacotherapy?
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What is pharmacodynamics?
The study of how drugs affect the body.
What factors affect drug action?
Define potency in pharmacodynamics.
The amount of drug needed to produce a desired effect.
What is efficacy in drug action?
The maximum effect a drug can produce.
How do agonists work?
They activate receptors to produce a biological response.
What role do antagonists play?
They block receptors and prevent a biological response.
What is the therapeutic index?
The ratio between the toxic dose and effective dose of a drug.
Define bioavailability.
The proportion of a drug that enters circulation when introduced into the body.
What does half-life measure?
The time it takes for the concentration of a drug to reduce to half its initial value.
What is dose-response relationship?
The relationship between the dose of a drug and the magnitude of its pharmacological effect.
What can tolerance lead to in pharmacotherapy?
Reduced response to a drug after repeated use.
What is the significance of receptor phosphorylation?
It can alter receptor activity and signaling potency.
What are enzyme inhibitors?
Substances that decrease enzyme activity, affecting drug metabolism.
What effect do enzyme inducers have?
They increase enzyme activity, leading to faster drug metabolism.
What is the importance of clinical trials in pharmacodynamics?
They help evaluate the safety and efficacy of drug therapies.
Identify a key aspect of patient variability in drug response.
Genetic differences can affect drug metabolism and action.
What is the impact of age on pharmacodynamics?
Age affects drug absorption, distribution, metabolism, and excretion.
How can drug interactions alter therapeutic effects?
They can either enhance or diminish drug actions and side effects.
Define agonist-antagonist activity.
Drugs that activate some receptors while blocking others.
What is maximal efficacy?
The greatest intensity of effect that a drug can produce.
Explain the concept of selectivity in pharmacodynamics.
The ability of a drug to preferentially elicit responses from one receptor subtype over others.
What is the study of what the drug does to the body called?
Pharmacodynamics
What does pharmacokinetics study?
What the body does to the drug.
What processes are included in pharmacokinetics?
What are the four major questions pharmacodynamics answers?
What does 'action' refer to in pharmacodynamics?
The initial combination of the drug with its target molecule.
What does 'effect' refer to in pharmacodynamics?
The measurable change in physiological function from the drug's action.
What is the action of Captopril?
Inhibits angiotensin-converting enzyme (ACE).
What is the effect of Captopril?
Vasodilation, leading to a fall in blood pressure.
Why is it important to understand drug action?
Different drugs can produce the same effect via different mechanisms.
What is the common mechanism of drug action?
Inhibition of enzymes.
What are the main targets of drug action?
How can a drug alter biochemical reaction rates?
By modulating enzyme activity.
What types of proteins do most drugs target?
Functional proteins.
What are structural proteins?
Proteins that form the body's framework, e.g., collagen.
What happens when enzymes are inhibited by drugs?
The rate of biochemical reactions is altered.
Is stimulation of enzymes common in drug action?
No, it is rare.
What is competitive inhibition?
It's when an inhibitor competes with the substrate for the active site. Can be reversible or irreversible.
What types can competitive inhibition be?
What is noncompetitive inhibition?
It's when an inhibitor binds to an enzyme, reducing its activity regardless of the substrate concentration.
What is the function of an enzyme?
Enzymes act as catalysts to accelerate biochemical reactions.
What is an enzyme's catalytic site?
It's the active site where the substrate binds to undergo a reaction, similar to the blades of scissors.
What happens when a substrate binds to an enzyme?
The substrate undergoes a biochemical reaction to form a product.
What is the role of inhibitors in enzyme activity?
Inhibitors decrease enzyme activity by blocking the active site or altering enzyme shape.
How does reversible inhibition differ from irreversible inhibition?
What is one characteristic of a competitive inhibitor?
It structurally resembles the substrate and binds to the active site of the enzyme.
What is an example of an enzyme action?
An enzyme converting a substrate like glucose into glucose-6-phosphate.
What does enzyme velocity depend on?
The number of active enzyme molecules.
What is the Michaelis constant (kM)?
Substrate concentration at which half of the enzyme molecules are active.
What does Vmax represent?
Maximum rate of the enzyme-catalyzed reaction when fully saturated with substrate.
What happens at low substrate concentration?
Few enzymes are active.
What is competitive inhibition?
Inhibition where a drug resembles the substrate and competes for the same catalytic site.
Effect of competitive inhibition on kM?
kM increases because more substrate is needed for half-maximal enzyme activity.
What is reversible competitive inhibition?
Inhibitor binds weakly and can be displaced by substrate, Vmax remains unchanged.
Example of reversible competitive inhibitor?
Physostigmine inhibits cholinesterase and can be overcome by increasing acetylcholine.
What is irreversible competitive inhibition?
Inhibitor binds strongly and forms a covalent bond, cannot be displaced by substrate.
Effect of irreversible competitive inhibition on Vmax?
Vmax decreases because fewer active enzyme molecules are available.
Example of an irreversible competitive inhibitor?
Organophosphate compounds inhibit cholinesterase irreversibly.
What is noncompetitive inhibition?
Inhibitor binds to a different site on the enzyme, causing structural changes and Vmax decreases.
Effect of noncompetitive inhibition on kM?
kM remains unchanged.
Example of a noncompetitive inhibitor?
Aspirin inhibits cyclooxygenase (COX) noncompetitively.
Summary of reversible competitive inhibition?
Summary of irreversible competitive inhibition?
Summary of noncompetitive inhibition?
What do transport proteins do?
Control the movement of ions and molecules across biological membranes.
What are the main types of transport proteins?
What is the role of ion pumps?
Move ions against concentration gradients using ATP.
What is an example of an ion pump?
Na+/K+-ATPase pump – Maintains sodium and potassium balance.
What do carrier proteins do?
Utilize ion gradients created by pumps to transport substances.
Give an example of a carrier protein.
Na+/Cl- cotransporter in the renal tubules.
What function do ion channels serve?
Allow passive movement of ions down their electrochemical gradient.
How do drugs affect transport proteins?
They can inhibit or stimulate their activity.
What is the effect of digoxin on Na+/K+-ATPase?
What drug inhibits noradrenaline reuptake?
Cocaine - Blocks noradrenaline transporter (NET).
What do thiazide diuretics inhibit?
Inhibit Na+/Cl- cotransporter in the distal convoluted tubule.
What is the effect of omeprazole?
Inhibits H+/K+-ATPase enzyme, reducing gastric acidity.
How do SSRIs work?
Block serotonin reuptake, enhancing serotonergic transmission.
What is one mechanism of drug action related to receptors?
Modulating the activity of specialized macromolecules, usually proteins.
What does a receptor bind?
A drug or endogenous chemical messenger (e.g., hormone, neurotransmitter)
What is the function of receptors?
To recognize drug molecules and transduce their signals into biological effects
What happens when a drug binds to a receptor?
What is an agonist?
A substance that activates a receptor
What is an antagonist?
A substance that blocks a receptor
What type of response do receptors initiate?
A cellular response
What are endogenous chemical messengers?
Substances like hormones and neurotransmitters produced within the body
What is the role of a drug in receptor interactions?
To modulate biological effects by binding to receptors
Can drugs act as both agonists and antagonists?
Yes, based on their interaction with specific receptors
What determines the effect of a drug on a receptor?
Whether it acts as an agonist or antagonist
What is an agonist?
A substance that binds to a receptor and activates it, producing a biological response.
What is an antagonist?
A substance that binds to a receptor but does not activate it, preventing the action of an agonist.
What do agonists mimic?
The effect of endogenous substances.
What do antagonists block?
The effects of agonists.
What are ligand-gated ion channels?
Integral membrane proteins that form ion channels, opening upon agonist binding.
What happens when an agonist binds to ligand-gated ion channels?
The channel opens, allowing ions to cross the membrane.
Give an example of a ligand-gated ion channel.
Nicotinic acetylcholine receptor (nAChR).
What is the effect of acetylcholine binding to nAChR?
Opens the channel, allowing sodium in and potassium out, leading to muscle contraction.
What is an example of an agonist for nAChR?
Nicotine.
What is an example of an antagonist for nAChR?
Tubocurarine (causes muscle relaxation).
What are G-protein-coupled receptors?
Receptors coupled to intracellular G-proteins that modulate enzymes or ion channels.
What is the mechanism of G-protein-coupled receptors?
Agonist binds, activating G-protein, which modulates effectors.
What are the key second messengers involved in G-protein signaling?
Give an example of a G-protein-coupled receptor.
Beta-adrenergic receptor, activated by adrenaline.
What does the binding of adrenaline to beta receptors do?
Stimulates adenylate cyclase, increasing cAMP levels.
What are enzyme-linked receptors?
Transmembrane proteins with intrinsic enzymatic activity, activating upon ligand binding.
What type of receptor is the insulin receptor?
A tyrosine kinase receptor.
What happens when insulin binds to its receptor?
Activates tyrosine kinase, leading to phosphorylation of intracellular proteins.
Give a drug example that acts as an agonist at insulin receptors.
Recombinant human insulin.
What are intracellular receptors?
Receptors located in the cytoplasm or nucleus that bind lipid-soluble substances.
How do intracellular receptors affect cellular function?
By interacting with DNA to regulate gene transcription.
What kind of ligands activate intracellular receptors?
Lipid-soluble substances.
Give an example of an intracellular receptor ligand.
Steroid hormones like glucocorticoids.
What action does prednisolone have?
Acts on intracellular glucocorticoid receptors to suppress inflammation.
What does levothyroxine regulate?
Metabolism by acting on nuclear thyroid hormone receptors.
What is the response time for G-protein-coupled receptors?
Intermediate response (seconds), involving second messengers.
What defines enzyme-linked receptors?
Slow response (minutes to hours), mediated by phosphorylation cascades.
What is the response time for intracellular receptors?
Very slow response (hours to days).
What is the main function of ligand-gated ion channels?
Mediates ion fluxes for fast signaling.
What role do G-protein-coupled receptors play in signaling?
Involve second messengers for cellular responses.
How do enzyme-linked receptors facilitate cellular responses?
Through phosphorylation cascades over minutes to hours.
What type of response do intracellular receptors provide?
Provides very slow responses over hours to days.
What is a Full Agonist?
Produces the maximum possible response by fully activating receptors.
What is a Partial Agonist?
Binds to receptors but produces a submaximal response even at full occupancy.
How does a Partial Agonist act?
Can act as both an agonist and an antagonist depending on context.
What is an Inverse Agonist?
Binds to the same receptor as an agonist but induces an opposite response.
What is the function of an Antagonist?
Binds to the receptor without activating it, preventing agonist binding.
What are the two types of Antagonists?
How does Adrenaline function as a drug?
Acts as an agonist on beta receptors to increase heart rate.
What is the role of Propranolol?
Acts as a beta receptor antagonist to decrease heart rate and blood pressure.
How does Diazepam affect neurotransmission?
Enhances GABA receptor activity, increasing chloride ion influx and causing sedation.
What effect does Atropine have on the body?
Blocks muscarinic receptors, reducing secretions and dilating pupils.
What does Prednisolone activate?
Activates intracellular glucocorticoid receptors to produce anti-inflammatory effects.
What is the dose-response relationship?
It is the relationship between the dose of a drug and the magnitude of its effect.
What does the dose-response relationship help determine?
What are the two types of dose-response relationships?
Explain the graded dose-response relationship.
Response measured continuously; increases with dose (e.g. blood pressure response).
What happens in the linear region of the sigmoid curve?
Small dose increases result in large response increases.
What occurs in the plateau region of the dose-response curve?
Response reaches maximum (Emax); further increases won't enhance effect.
Define Emax.
The greatest effect produced by the drug regardless of dose.
What is EC50?
Concentration producing 50% of maximum response; indicates potency.
What does a steep slope indicate on the dose-response curve?
Small dose changes lead to large effect changes.
Differentiate between efficacy and potency.
What is the receptor occupancy theory?
Response is proportional to the fraction of receptors occupied.
Describe the quantal dose-response relationship.
All-or-none response representing percentage of a population showing effect.
Example of a quantal response?
Percentage of subjects falling asleep with varying sedative doses.
Graphing which relationship uses a logarithmic scale?
Both graded and quantal dose-response relationships.
What shape does the curve take when drug sensitivity data is plotted?
A sigmoid (S-shaped) curve.
What does the y-axis represent when plotting drug sensitivity data?
The distribution of sensitivity to the drug.
What type of curve is obtained when data is plotted?
A frequency distribution curve.
What does a sigmoid curve indicate in drug sensitivity studies?
Intermediate sensitivity levels among subjects.
What is ED50?
The dose producing the desired effect in 50% of the population.
What does TD50 represent?
The dose producing a toxic effect in 50% of the population.
What is the definition of LD50?
The dose causing death in 50% of experimental animals.
What is the Therapeutic Index (TI)?
The ratio of TD50 to ED50; indicates drug safety.
What does a high TI indicate?
The drug is relatively safe; toxic dose is much higher than effective dose.
What does a low TI signify?
The drug is potentially dangerous; effective and toxic doses are close.
Which drug has a high TI?
Penicillin; considered very safe.
Which drugs have low TIs?
Digoxin, lithium, warfarin; require close monitoring.
What is the therapeutic window?
The range between minimum effective concentration (MEC) and minimum toxic concentration (MTC).
What defines narrow therapeutic windows?
Require frequent plasma level monitoring to avoid toxicity.
How does body weight affect drug dosage?
Doses are calculated per kilogram; larger mass = higher doses.
How do lipophilic drugs distribute in obese individuals?
They accumulate in adipose tissue, causing prolonged effects.
What are the drug metabolism effects in newborns?
Reduced liver and kidney function; careful dose adjustments needed.
What syndrome can chloramphenicol cause in infants?
Gray baby syndrome; due to immature metabolism.
What age-related change affects the elderly?
Reduced renal clearance and liver metabolism; sensitivity to drugs increases.
How do hormonal differences affect drug metabolism in sexes?
Women may metabolize drugs (e.g., alcohol) slower.
How does pregnancy impact pharmacokinetics?
Increased plasma volume, renal clearance, and protein binding changes.
What toxicity can occur in cats with certain drugs?
Inability to metabolize paracetamol efficiently; leads to toxicity.
How do genetic factors alter drug response?
Variations in enzymes and receptors can significantly influence outcomes.
What is an example of a pharmacogenetic variation?
Slow and fast acetylators affect isoniazid metabolism.
How can G6PD deficiency affect drug use?
Increases risk of hemolysis with certain drugs like primaquine.
What can happen when increasing doses of a medication are required?
May require increasing doses to maintain the same effect.
Name examples of medications that may require increasing doses.
What is tachyphylaxis?
A rapid decrease in drug response after a few doses in quick succession.
Give examples of drugs that show tachyphylaxis.
What causes tachyphylaxis in ephedrine and tyramine?
Depletion of stored noradrenaline.
What occurs in drug interactions?
When two or more drugs affect each other's action.
What are pharmacodynamic interactions?
What are pharmacokinetic interactions?
How does aspirin influence the effect of warfarin?
What effect does rifampicin have on oral contraceptives?
What effect does erythromycin have on theophylline?
What environmental factors can modify drug action?
How does high environmental temperature affect drug action?
What is the placebo effect?
Which substances can affect enzyme induction?
How can psychological factors influence drug responses?
What is drug antagonism?
A phenomenon where the effect of one drug is inhibited by another drug.
What is synergism?
When two drugs enhance each other's effects.
When can antagonism be beneficial?
To counteract poisoning or overdose (e.g., naloxone with morphine).
When can antagonism be harmful?
When an essential therapeutic effect is blocked (e.g., beta-blockers with beta-agonists).
What are the types of drug antagonism?
What is physical antagonism?
When two drugs physically oppose each other's actions without chemical reaction.
Give an example of physical antagonism.
What is chemical antagonism?
When two substances chemically react to form an inactive product.
Give an example of chemical antagonism.
What is physiological antagonism?
When drugs act on different receptors but produce opposite effects.
Give an example of physiological antagonism.
What is pharmacological antagonism?
Occurs when two drugs act on the same receptor system; antagonists block agonists.
What is competitive antagonism?
Antagonist competes with agonist for the same receptor site, reversible binding.
What results from competitive antagonism?
Maximum response remains the same; EC50 increases with higher agonist doses.
What is the difference between competitive and non-competitive antagonism?
Competitive antagonism is reversible; non-competitive cannot be overcome by increasing agonist concentration.
What effect does a 50% increase in dose have on the dose-response curve?
Shifts to the right.
What does atropine do at muscarinic receptors?
What is the effect of propranolol at β-adrenergic receptors?
How does mepyramine affect H1-receptors?
What characterizes irreversible antagonism?
What binds irreversibly to receptors?
What happens to Emax in irreversible binding?
What happens to EC50 in irreversible binding?
What is an example of an irreversible antagonist?
What characterizes non-competitive antagonism?
What is the result of non-competitive antagonism?
What is an example of a non-competitive antagonist?
What is a partial agonist?
What happens when a partial agonist is administered with a full agonist?
What is an example of a partial agonist?
What is an inverse agonist?
What do inverse agonists stabilize?
What are examples of inverse agonists?
What is drug synergism?
What is additive synergism?
What is supra-additive synergism?
What is a clinical use of antagonism?
What are beta-blockers used for?
What is the significance of understanding antagonism?
What types of mechanisms can lead to antagonism?
What produces effects by binding to receptors?
Drugs
What does affinity refer to?
The ability of a drug to bind to its receptor
What is potency a measure of?
How much drug is required to produce a given effect
What does efficacy determine?
The maximum effect (Emax) a drug can produce
What type of agonist has both high affinity and high efficacy?
Full agonist
Which agonist produces a submaximal response?
Partial agonist
What is an example of a full agonist?
Morphine
What does an antagonist do?
Binds to the receptor without activating it and blocks agonist actions
What is the main premise of Occupation Theory?
The response is directly proportional to the number of receptors occupied
What does Rate Theory emphasize?
The rate of drug-receptor interaction
What happens when all receptors are occupied according to Occupation Theory?
Maximum effect (Emax) occurs
What are the limitations of Occupation Theory?
What happens with drugs that associate and dissociate rapidly?
Produce stronger effects
What is an example of an inverse agonist?
Propranolol
How does a partial agonist act in the presence of a full agonist?
Can act as an antagonist
What is the term for the concentration producing 50% of maximum response?
EC50
What type of receptor activity do inverse agonists target?
Constitutive activity
What does high affinity enable for a drug?
Bind tightly even at low concentrations
Which phenomenon cannot be explained by Rate Theory?
Long-lasting effects of irreversible binding drugs
What are the two states of receptors according to modern receptor theory?
Can receptors exist in the active state without a ligand?
Yes, a small fraction of receptors may spontaneously exist in the active state even without a ligand.
What does 'R' represent in receptor theory?
R represents the inactive state of a receptor.
What does 'R*' represent in receptor theory?
R* represents the active state of a receptor.
What is the significance of interconvertible states of receptors?
It allows receptors to switch between inactive and active states, affecting signaling.
What concept is highlighted by spontaneous receptor activation?
It highlights the dynamic nature and efficiency of receptor signaling.
What shifts equilibrium toward activation in receptors?
Agonists have higher affinity for R*.
What stabilizes the inactive state of a receptor?
Inverse agonists have higher affinity for R.
What is the effect of neutral antagonists?
They have equal affinity for R and R* and block both activities.
What concept explains constitutive receptor activity?
Constitutive activity occurs with drug interactions that affect receptor states.
What defines spare receptors?
A receptor system has spare receptors when Emax is achieved without occupying all receptors.
How does spare receptor concept relate to cardiac muscle?
Maximal response to adrenaline can occur with only partial occupancy of ẞ1-receptors.
What is the impact of irreversible antagonists in relation to spare receptors?
Emax may not decrease until receptor reserve is exhausted.
What influences receptor number and sensitivity?
They can be upregulated or downregulated by various influences.
What leads to upregulation of receptors?
Prolonged exposure to antagonists or deficiency of agonist.
What is an example of upregulation effects?
Chronic ẞ-blocker use may cause rebound tachycardia upon withdrawal.
What causes downregulation of receptors?
Prolonged exposure to agonists results in downregulation.
What is receptor-effector coupling?
It describes the relationship between receptor activation and cellular response.
How does coupling efficiency affect drug response?
Efficiently coupled drugs produce strong effects with limited activation.
What is the cyclic AMP (cAMP) pathway?
Activated by ẞ1- and ẞ2-adrenergic receptors, increases cAMP and activates PKA.
What is the role of protein kinase A (PKA)?
PKA phosphorylates target proteins leading to various physiological effects.
What triggers the phosphatidylinositol pathway?
Gq-protein-coupled receptors lead to formation of IP3 and DAG.
What does DAG cause in cells?
DAG leads to Ca²+ release and activation of protein kinase C (PKC).
What is the role of nitric oxide (NO) in signaling?
NO activates the cyclic GMP pathway, mediating smooth muscle relaxation.
How is ion channel modulation achieved?
Ligand-gated channels open/close upon ligand binding, affecting membrane potential.
What describes pharmacodynamics?
Pharmacodynamics involves how drugs act on the body, including efficacy and receptor interactions.
What is the difference between action and effect in pharmacology?
What are the types of membrane receptors?
What differentiates agonists from antagonists?
What do dose-response relationships define?
What does potency refer to?
The amount of drug needed to produce an effect.
What is efficacy in pharmacology?
The maximum effect a drug can produce.
What does therapeutic index (TI) indicate?
The safety margin of a drug; a ratio comparing the effective dose to the toxic dose.
What factors modify drug action?
What types of antagonism exist?
What are the theories of drug action?
What does binding translate into?
What forms the foundation for rational pharmacotherapy?
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