Pharmacokinetic-pharmacodynamic (PK-PD) interactions MCQs With Answer

Pharmacokinetic-pharmacodynamic (PK-PD) interactions MCQs With Answer

Understanding PK-PD relationships is essential for rational drug design, dose selection, and therapeutic optimization in M.Pharm practice. This quiz collection focuses on how absorption, distribution, metabolism, and excretion (PK) interact with drug action and response (PD). Questions cover classical models (Emax, sigmoid Emax), PK/PD indices for antimicrobials, link and effect‑compartment models, hysteresis, indirect response models, target‑mediated drug disposition, variability, and practical applications like dose optimization and biomarker use. These MCQs emphasize conceptual depth and applied problem solving to reinforce modeling concepts, interpretation of PK/PD parameters, and translation into clinical dosing strategies for postgraduate students.

Q1. Which PK-PD index is most predictive of efficacy for time-dependent antibiotics?

• Peak concentration to MIC ratio (Cmax/MIC)
• Area under the concentration-time curve to MIC ratio (AUC/MIC)
• Time above MIC (T>MIC)
• Minimum inhibitory concentration alone (MIC)

Correct Answer: Time above MIC (T>MIC)

Q2. In an Emax model, what does EC50 represent?

• The maximum obtainable effect
• The baseline effect before drug administration
• The concentration producing half of Emax
• The slope factor determining steepness

Correct Answer: The concentration producing half of Emax

Q3. A counter-clockwise hysteresis loop in a plasma concentration-effect plot typically indicates which phenomenon?

• Acute tolerance or tachyphylaxis
• Time delay between plasma concentration and effect due to distribution to effect site
• Irreversible receptor binding
• Metabolite-mediated potentiation of effect

Correct Answer: Time delay between plasma concentration and effect due to distribution to effect site

Q4. The sigmoid Emax model incorporates which parameter to describe steepness of the concentration-effect curve?

• EC50
• n (Hill coefficient)
• E0
• Ke0

Correct Answer: n (Hill coefficient)

Q5. In a PK-PD link model with an effect compartment, what does the parameter ke0 represent?

• Elimination rate constant from plasma
• Rate constant for equilibration between plasma and effect site
• Maximum effect achievable
• Baseline effect in absence of drug

Correct Answer: Rate constant for equilibration between plasma and effect site

Q6. Which statement best describes target-mediated drug disposition (TMDD)?

• Linear clearance irrespective of concentration
• Nonlinear PK due to high-affinity binding to pharmacologic target affecting distribution and clearance
• PK governed only by renal filtration
• Drug distribution limited exclusively by plasma protein binding

Correct Answer: Nonlinear PK due to high-affinity binding to pharmacologic target affecting distribution and clearance

Q7. An indirect response model that describes drug inhibition of the production of an endogenous mediator uses which basic structure?

• Direct proportional effect to plasma concentration
• Drug stimulates elimination of mediator
• Drug inhibits the zero-order production rate (kin) of the mediator
• Drug irreversibly binds to receptor causing permanent loss of mediator

Correct Answer: Drug inhibits the zero-order production rate (kin) of the mediator

Q8. In population PK-PD modeling, which source of variability is captured by adding a between-subject variability term to parameters?

• Residual unexplained variability in observations
• Systematic assay bias only
• Interindividual differences in parameters due to physiology, genetics, covariates
• Random within-subject measurement noise only

Correct Answer: Interindividual differences in parameters due to physiology, genetics, covariates

Q9. Which PK-PD index correlates best with efficacy of concentration-dependent antibiotics like aminoglycosides?

• Time above MIC (T>MIC)
• Area under the curve (AUC) alone
• Peak to MIC ratio (Cmax/MIC)
• Steady-state trough concentration

Correct Answer: Peak to MIC ratio (Cmax/MIC)

Q10. What is the primary purpose of using an effect compartment (biophase) in PK-PD modeling?

• To model metabolite formation rates
• To account for delay between plasma concentrations and observed effect without altering plasma PK
• To force linear kinetics on non-linear drugs
• To represent drug-protein binding in plasma

Correct Answer: To account for delay between plasma concentrations and observed effect without altering plasma PK

Q11. Which parameter combination defines potency and efficacy respectively in a typical PD model?

• EC50 and Emax
• Emax and EC50
• Ke0 and E0
• Cmax and AUC

Correct Answer: EC50 and Emax

Q12. A clockwise hysteresis loop between concentration and effect is commonly indicative of:

• Indirect response with slow turnover
• Formation of an active metabolite that lags behind parent drug
• Rapid tolerance or acute desensitization reducing effect at higher concentrations
• Progressive sensitization increasing effect over time

Correct Answer: Rapid tolerance or acute desensitization reducing effect at higher concentrations

Q13. In Monte Carlo simulations for antimicrobial PK/PD, what is typically being simulated?

• Random selection of assay reagents
• Variability in patient PK, MIC distribution and probability of target attainment across a population
• Only a single individual’s time course repeatedly
• Protein binding changes in vitro exclusively

Correct Answer: Variability in patient PK, MIC distribution and probability of target attainment across a population

Q14. Which of the following best describes E0 in PK-PD models?

• The maximal effect achievable by the drug
• The baseline effect in absence of drug
• The rate constant of elimination from effect site
• The EC90 value

Correct Answer: The baseline effect in absence of drug

Q15. When a metabolite contributes to pharmacologic effect, which modeling approach is most appropriate?

• Ignore the metabolite and model parent only
• Use a combined parent-metabolite PK-PD model linking metabolite concentrations to effect
• Assume additive clearance of parent and metabolite without PD linkage
• Model only metabolite kinetics and ignore parent drug

Correct Answer: Use a combined parent-metabolite PK-PD model linking metabolite concentrations to effect

Q16. Which approach helps distinguish between pharmacokinetic delay and indirect pharmacodynamic mechanism when an effect lags behind concentration?

• Perform only single time-point measurements
• Fit both effect‑compartment (ke0) models and indirect response models and compare fits and parameter plausibility
• Assume the lag is due to assay error
• Use only noncompartmental analysis

Correct Answer: Fit both effect‑compartment (ke0) models and indirect response models and compare fits and parameter plausibility

Q17. In PK-PD, the Hill coefficient greater than 1 indicates:

• A linear relationship between concentration and effect
• Negative cooperativity at the receptor
• Positive cooperativity or steeper concentration-effect curve
• No effect of concentration on response

Correct Answer: Positive cooperativity or steeper concentration-effect curve

Q18. Which covariate is least likely to be included to explain interindividual variability in a PK-PD model for an oral drug?

• Renal function (e.g., creatinine clearance)
• Body weight or body surface area
• Genetic polymorphism of metabolic enzyme
• Study site color of building

Correct Answer: Study site color of building

Q19. For concentration-dependent killing antibiotics, what dosing strategy is typically recommended to maximize bactericidal effect while minimizing toxicity?

• Frequent small doses to maximize T>MIC
• High intermittent doses to maximize Cmax/MIC with adequate AUC
• Continuous infusion to maintain steady low concentrations
• No dosing adjustments based on PK-PD

Correct Answer: High intermittent doses to maximize Cmax/MIC with adequate AUC

Q20. Which software tool is commonly used for nonlinear mixed-effects population PK-PD modeling in M.Pharm research?

• GraphPad Prism only
• Microsoft Excel with no add-ons
• NONMEM or alternatives like Monolix and nlmixr
• ImageJ for PK-PD fitting

Correct Answer: NONMEM or alternatives like Monolix and nlmixr

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