Q.1 What does pharmacodynamics primarily study?
The absorption of drugs in the body
The effects of drugs on the body
The metabolism of drugs
The excretion of drugs
Explanation - Pharmacodynamics deals with the biochemical and physiological effects of drugs and their mechanisms of action.
Correct answer is: The effects of drugs on the body
Q.2 Which term describes the maximum effect a drug can produce regardless of dose?
Potency
Efficacy
Affinity
Selectivity
Explanation - Efficacy refers to the maximum response achievable from a drug, while potency refers to the dose required to produce an effect.
Correct answer is: Efficacy
Q.3 A drug that binds to a receptor and produces a maximal response is called:
Partial agonist
Full agonist
Antagonist
Inverse agonist
Explanation - A full agonist binds to a receptor and produces 100% of the possible effect.
Correct answer is: Full agonist
Q.4 Which of the following binds to a receptor and prevents its activation?
Agonist
Antagonist
Partial agonist
Allosteric activator
Explanation - Antagonists bind to receptors without activating them, blocking agonists from binding.
Correct answer is: Antagonist
Q.5 The relationship between drug concentration and effect is usually depicted as a:
Michaelis-Menten curve
Dose-response curve
Titration curve
Survival curve
Explanation - A dose-response curve shows how the effect of a drug changes with different concentrations or doses.
Correct answer is: Dose-response curve
Q.6 Potency of a drug is determined by:
Maximum effect produced
Dose required to produce a specific effect
Binding to plasma proteins
Route of administration
Explanation - Potency refers to the amount of drug needed to produce a given effect; lower dose means higher potency.
Correct answer is: Dose required to produce a specific effect
Q.7 A partial agonist:
Produces no effect
Produces a full effect
Produces a submaximal effect even at full receptor occupancy
Blocks receptor activity
Explanation - Partial agonists activate receptors but cannot elicit the maximum response possible.
Correct answer is: Produces a submaximal effect even at full receptor occupancy
Q.8 Competitive antagonism can be overcome by:
Increasing the antagonist dose
Increasing the agonist dose
Changing the receptor
Increasing metabolism
Explanation - In competitive antagonism, agonists and antagonists compete for the same receptor, so higher agonist concentrations can overcome inhibition.
Correct answer is: Increasing the agonist dose
Q.9 Which type of antagonist binds irreversibly to a receptor?
Competitive antagonist
Non-competitive antagonist
Partial agonist
Inverse agonist
Explanation - Non-competitive antagonists bind irreversibly or allosterically, reducing maximal response regardless of agonist dose.
Correct answer is: Non-competitive antagonist
Q.10 The slope of the dose-response curve indicates:
Efficacy
Potency
Receptor reserve
Affinity
Explanation - A steeper slope can indicate a high receptor reserve or cooperative interactions among receptors.
Correct answer is: Receptor reserve
Q.11 Allosteric modulators act by:
Binding at the active site
Binding at a site other than the active site
Blocking metabolism
Increasing renal excretion
Explanation - Allosteric modulators bind to sites other than the main receptor site and modify receptor activity.
Correct answer is: Binding at a site other than the active site
Q.12 Therapeutic index measures:
Drug efficacy
Safety margin of a drug
Potency
Duration of action
Explanation - Therapeutic index is the ratio between toxic dose and effective dose; higher TI indicates a safer drug.
Correct answer is: Safety margin of a drug
Q.13 Which is an example of an inverse agonist effect?
Activating a receptor
Reducing receptor activity below basal level
Blocking a receptor
Increasing enzyme metabolism
Explanation - Inverse agonists decrease constitutive receptor activity, producing effects opposite to agonists.
Correct answer is: Reducing receptor activity below basal level
Q.14 The EC50 value represents:
Dose at which 50% of subjects respond
Concentration producing 50% of maximal effect
Concentration producing maximum effect
Dose producing toxic effect in 50% subjects
Explanation - EC50 is a measure of drug potency, indicating the concentration needed for 50% of maximal response.
Correct answer is: Concentration producing 50% of maximal effect
Q.15 Receptor desensitization occurs due to:
Prolonged exposure to an agonist
Competitive antagonism
Metabolic activation
Renal excretion
Explanation - Continuous stimulation of receptors can reduce responsiveness through desensitization or downregulation.
Correct answer is: Prolonged exposure to an agonist
Q.16 Which receptor property determines the strength of drug binding?
Affinity
Efficacy
Potency
Selectivity
Explanation - Affinity reflects how tightly a drug binds to its receptor, influencing its ability to produce an effect.
Correct answer is: Affinity
Q.17 The concept of spare receptors explains why:
Maximal effect may occur without all receptors being occupied
Potency is high
Efficacy is low
Drugs are metabolized faster
Explanation - Spare receptors allow a full response even if only a fraction of receptors are activated.
Correct answer is: Maximal effect may occur without all receptors being occupied
Q.18 Which type of dose-response curve is used for quantal effects?
Graded dose-response curve
Quantal dose-response curve
Michaelis-Menten curve
Sigmoidal enzyme curve
Explanation - Quantal dose-response curves show the distribution of doses producing a specified effect in a population.
Correct answer is: Quantal dose-response curve
Q.19 Which statement about non-competitive antagonists is correct?
They shift the dose-response curve rightward without changing max effect
They decrease the maximal response
They increase agonist potency
They only act at high doses
Explanation - Non-competitive antagonists reduce the maximal effect because they cannot be overcome by increasing agonist concentration.
Correct answer is: They decrease the maximal response
Q.20 An agonist with high potency but low efficacy will:
Produce a maximal effect at low dose
Produce submaximal effect even at high dose
Have no effect
Act as an antagonist
Explanation - High potency refers to low dose required, but low efficacy limits the maximum effect achievable.
Correct answer is: Produce submaximal effect even at high dose
Q.21 The Kd (dissociation constant) of a drug is:
Concentration of drug producing half-maximal effect
Affinity of drug for receptor
Dose producing toxic effect
Measure of efficacy
Explanation - Kd indicates the concentration of drug at which 50% of receptors are occupied; lower Kd means higher affinity.
Correct answer is: Affinity of drug for receptor
Q.22 Selectivity of a drug refers to:
Ability to produce only desired effect
Maximal effect achievable
Dose required to produce effect
Metabolism speed
Explanation - Selective drugs preferentially act on specific receptors or tissues, reducing side effects.
Correct answer is: Ability to produce only desired effect
Q.23 Which effect is NOT part of pharmacodynamics?
Drug-receptor interaction
Dose-response relationship
Drug metabolism
Therapeutic and toxic effects
Explanation - Drug metabolism is part of pharmacokinetics, not pharmacodynamics.
Correct answer is: Drug metabolism
Q.24 Tachyphylaxis is defined as:
Sudden increase in drug effect
Rapid decrease in response to a drug after repeated doses
Slow accumulation of drug
Drug allergy
Explanation - Tachyphylaxis is a rapid form of desensitization where the response diminishes quickly after repeated administration.
Correct answer is: Rapid decrease in response to a drug after repeated doses