Pharmacology Chapter on Drug-Receptor Interactions
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Questions and Answers

What is the primary reason a drug does not affect a cell?

  • The cell does not express the receptor for the drug. (correct)
  • The drug was administered too frequently.
  • The drug was not administered correctly.
  • The drug concentration was too high.

    • Which statement about the drug-receptor complex is true?

  • The binding of a drug is specific to the receptor it targets. (correct)
  • The drug acts independently of the receptor concentration.
  • The drug-receptor complex forms through an irreversible reaction.
  • The concentration of drug in the biophase does not affect receptor occupancy.

    • According to the Receptor Occupancy Theory, what happens when all receptors are occupied?

  • The drug concentration becomes ineffective.
  • A partial effect will still be observed.
  • The maximum drug effect is achieved. (correct)
  • None of the receptors can bind additional drugs.

    • What might occur when a drug binds to its receptor?

    <p>It may block the receptor, preventing the natural message from being received.</p> Signup and view all the answers

    The equilibrium dissociation constant (KD) is important because it indicates what?

    <p>The concentration of drug at which half of the receptors are occupied.</p> Signup and view all the answers

    What type of receptor is the GABA~A~ receptor classified as?

    <p>Ion Channel</p> Signup and view all the answers

    What effect does binding of adrenaline to β1-adrenergic receptors have?

    <p>Increases heart contractility</p> Signup and view all the answers

    Which of the following is an example of a classical receptor?

    <p>Neurotransmitter receptors</p> Signup and view all the answers

    What characteristic of drugs determines their ability to bind to the correct receptors?

    <p>Chemical selectivity</p> Signup and view all the answers

    Which of the following interactions forms a drug-receptor complex?

    <p>Reversible chemical reaction</p> Signup and view all the answers

    What principle explains the relationship between drug concentration and biological effect?

    <p>Law of Mass Action</p> Signup and view all the answers

    Which type of drug target works by inhibiting or promoting the activity of transport proteins?

    <p>Carrier proteins</p> Signup and view all the answers

    Which of the following drugs acts as a Na+ channel blocker?

    <p>Lidocaine</p> Signup and view all the answers

    What is the primary effect of glucocorticoids on glucose levels in the bloodstream?

    <p>Mobilize glucose from the liver to the bloodstream</p> Signup and view all the answers

    Under what condition does synergism occur between two drugs?

    <p>The combined effect is greater than the sum of the individual effects.</p> Signup and view all the answers

    Which of the following statements best describes summation in drug effects?

    <p>The combined effect equals the algebraic sum of their individual effects.</p> Signup and view all the answers

    What role does a synergist play when combined with another drug?

    <p>It increases the concentration of the other drug at receptor sites.</p> Signup and view all the answers

    In the context of drug interactions, what distinguishes additivity from summation?

    <p>Additivity requires drugs to share the same mechanism, while summation does not.</p> Signup and view all the answers

    What is the primary characteristic of non-competitive antagonism?

    <p>It binds to a different site on the receptor.</p> Signup and view all the answers

    Which of the following best describes the effects of a reduction in the number of spare receptors in a system?

    <p>It requires 100% receptor occupancy to reach maximal response.</p> Signup and view all the answers

    What mechanism does phenoxybenzamine use as an antagonist?

    <p>It binds irreversibly to α-adrenoceptors.</p> Signup and view all the answers

    What type of antagonism occurs when an antagonist binds to the agonist in solution?

    <p>Chemical antagonism</p> Signup and view all the answers

    Which of the following drugs exemplifies non-competitive antagonism?

    <p>Picrotoxin</p> Signup and view all the answers

    What result occurs due to chemical antagonism?

    <p>An inactive complex is formed with the agonist.</p> Signup and view all the answers

    Which describes a situation in a system without spare receptors?

    <p>There is a complete blockage of receptor function.</p> Signup and view all the answers

    What effect does an irreversible antagonist have on the dose-response curve?

    <p>It alters the slope of the curve.</p> Signup and view all the answers

    What characterizes competitive antagonism?

    <p>Agonist and antagonist compete for the same receptor binding site.</p> Signup and view all the answers

    What occurs in reversible antagonism when the agonist concentration increases?

    <p>The agonist can completely displace the antagonist.</p> Signup and view all the answers

    Which of the following statements is true regarding irreversible antagonism?

    <p>A fraction of receptors becomes permanently unavailable for agonist binding.</p> Signup and view all the answers

    Which effect occurs on the agonist log D-R curve due to reversible antagonism?

    <p>A parallel shift to the right without loss of maximum response.</p> Signup and view all the answers

    How do receptor affinities and concentrations relate in competitive antagonism?

    <p>They determine the fraction of receptors occupied by the drugs.</p> Signup and view all the answers

    What happens to the agonist's effect when the antagonist is present in irreversible antagonism?

    <p>The agonist effect is reduced permanently.</p> Signup and view all the answers

    Why can't antagonism be overcome in irreversible antagonism?

    <p>The antagonist binds irreversibly, often through covalent bonding.</p> Signup and view all the answers

    In competitive antagonism, which substance can shift the agonist response back to maximal levels?

    <p>Increasing the agonist concentration.</p> Signup and view all the answers

    What is the primary action of benzodiazepines like diazepam in the treatment of anxiety?

    <p>Increase GABA channel responsiveness</p> Signup and view all the answers

    What does 'cross-tolerance' refer to in the context of drug responsiveness?

    <p>Tolerance to one drug affecting sensitivity to another drug in the same class</p> Signup and view all the answers

    What distinguishes 'tachyphylaxis' from 'acquired tolerance'?

    <p>Tachyphylaxis develops rapidly, whereas acquired tolerance develops slowly over weeks</p> Signup and view all the answers

    Which type of variation describes different responses to the same drug among different patients?

    <p>Inter-patient variation</p> Signup and view all the answers

    What are common possible consequences of drug responsiveness variation?

    <p>Lack of efficacy for some patients</p> Signup and view all the answers

    What mechanism may directly affect variability in drug responsiveness?

    <p>Pharmacokinetic factors influencing ADME processes</p> Signup and view all the answers

    What defines 'hypo-responsiveness' in the context of drug response?

    <p>Progressively decreasing responsiveness to a drug</p> Signup and view all the answers

    What is a potential qualitative variation in drug response?

    <p>Having an unexpected and serious side effect from a drug</p> Signup and view all the answers

    Study Notes

    Pharmacology Outline

    • Pharmacology is the study of drug-body interactions
    • It involves drug actions on the body and the body's actions on the drug

    Drug-Receptor Concepts

    • Drugs interact with biological systems by mimicking or affecting natural chemical messengers (e.g., neurotransmitters, hormones)
    • Two types of drug action exist:
      • Non-specific drug action involves simple physical or chemical reactions, such as antacids neutralizing acid, osmotic diuretics increasing solute content
      • Specific drug action involves drugs interacting with macromolecules/cellular targets (receptors)
    • Receptors are protein or glycoprotein molecules whose configuration determines their role
    • Drugs interact with receptors to form a drug-receptor complex, a reversible chemical reaction
    • This interaction is governed by the law of mass action

    Drug-Receptor Interactions

    • The drug-receptor interaction is a reversible chemical reaction
    • The fraction of receptors occupied by the drug depends on drug concentration and equilibrium dissociation constant(KD)
    • The biological effect is directly proportional to the fraction of receptors occupied by the drug.

    Drug Concentration-Effect Curve

    • The maximal effect (Emax) occurs when all receptors are occupied.
    • The graph shows a relationship between drug concentration and fractional receptor occupancy
    • Relationship between drug concentration and maximal effect illustrated.
    • The graph demonstrates a concentration-response curve showing increase of the response, the rate of response, and the maximum response

    Log Drug Concentration

    • Relationship between drug concentration and receptor occupancy is logarithmic.
    • Four possible consequences of drug-receptor interactions may happen:
      • Mimic natural chemical messenger
      • Block natural chemical messenger
      • Influence the binding of a natural chemical messenger -Produce opposite effect of a natural chemical messenger.

    Agonism and Antagonism

    • Agonists bind to receptors, activate them, and elicit a biological response.
      • Full agonists produce the maximum possible response.
      • Partial agonists produce less than the maximum response.
    • Antagonists bind to receptors but do not activate them, preventing the binding of agonists.
      • Competitive antagonists compete with agonists for the same binding site.
      • Non-competitive antagonists bind to a different site, reducing maximal response and not surmountable
      • Chemical antagonists directly inactivate an agonist.
    • Physiological antagonism involves opposing effects from different receptors.
    • Pharmacokinetic antagonism reduces the concentration of the agonist (by altering absorption, metabolism or excretion)

    Synergism and Potentiation

    • Synergism occurs when the combined effect of drugs is greater than the sum of their individual effects.

    Variation in Drug Responsiveness

    • Drug response can vary between patients and within the same patient.
    • Variations are classified as qualitative, quantitative, hyper-responsiveness and hypo-responsiveness/tolerance.
    • Drug tolerance is the diminished response to a drug after repeated exposure.

    Clinical Selectivity

    • Absolute selectivity implies a drug affects only one specific site.
    • Relative selectivity describes the preferential effect to one site versus other possible sites of action.

    Therapeutic Index

    • The therapeutic index is the ratio of the toxic dose to the effective dose.
    • It measures margin of safety for a drug.

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    Drug-Receptor Concepts (PDF)

    Description

    Test your knowledge on the principles of pharmacology, specifically focusing on drug-receptor interactions and the mechanisms of action. This quiz covers key concepts like receptor occupancy theory, types of receptors, and the effect of various drugs on biological systems.

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