Pharmacokinetic/pharmacodynamic correlation in therapy MCQs With Answer

Pharmacokinetic/pharmacodynamic correlation in therapy MCQs With Answer

This question set is designed for M.Pharm students to deepen understanding of pharmacokinetic–pharmacodynamic (PK/PD) relationships and their application in therapeutic drug monitoring (TDM) and dose optimization. The MCQs cover core concepts—PK/PD indices (AUC/MIC, Cmax/MIC, %T>MIC), concentration- vs time-dependent effects, free drug considerations, steady state and loading doses, population PK, Monte Carlo simulations, and clinical adjustment strategies in renal/hepatic impairment. Each question emphasizes interpretation of PK/PD data and practical decision-making for safer, more effective therapy. Use these questions to test critical thinking and readiness for clinical pharmacokinetics practice.

Q1. What is the fundamental goal of pharmacokinetic/pharmacodynamic (PK/PD) correlation in therapy?

• To predict adverse drug reactions based on patient history
• To relate drug exposure to pharmacologic effect and optimize dosing
• To design novel drug molecules with improved potency
• To standardize laboratory assay methods for drug measurement

Correct Answer: To relate drug exposure to pharmacologic effect and optimize dosing

Q2. Which PK/PD index is most predictive of efficacy for aminoglycoside antibiotics?

• % Time the drug concentration exceeds MIC (%T>MIC)
• AUC over 24 hours divided by MIC (AUC24/MIC)
• Peak concentration divided by MIC (Cmax/MIC)
• Minimum inhibitory concentration alone (MIC)

Correct Answer: Peak concentration divided by MIC (Cmax/MIC)

Q3. For a time-dependent antibiotic such as a beta-lactam, which dosing strategy maximizes bacterial killing?

• Single large bolus dose once daily to maximize Cmax
• Prolonged or continuous infusion to maximize %T>MIC
• Intermittent high peaks with long dosing intervals
• Decreasing doses to reduce toxicity risk

Correct Answer: Prolonged or continuous infusion to maximize %T>MIC

Q4. In TDM, why is unbound (free) drug concentration often more relevant than total concentration?

• Free drug concentrations are easier to measure in routine labs
• Only unbound drug is pharmacologically active and able to cross membranes
• Total concentration does not change with dose adjustments
• Protein binding always increases toxicity and must be minimized

Correct Answer: Only unbound drug is pharmacologically active and able to cross membranes

Q5. Which PK parameter primarily determines the time to reach steady state for a drug given at regular intervals?

• Volume of distribution (Vd)
• Clearance (Cl)
• Elimination half-life (t1/2)
• Bioavailability (F)

Correct Answer: Elimination half-life (t1/2)

Q6. When is a loading dose indicated in PK/PD-guided therapy?

• When a drug has a very short half-life and rapid onset is unnecessary
• When immediate attainment of target concentration is required due to long half-life
• Only for drugs administered orally to increase absorption
• When clearance is very high and frequent maintenance doses are planned

Correct Answer: When immediate attainment of target concentration is required due to long half-life

Q7. A drug exhibits non-linear (capacity-limited) elimination. Which statement is correct for PK/PD considerations?

• Doubling the dose will always double the plasma concentration
• Small dose changes can cause disproportionate concentration changes; monitoring is essential
• Half-life remains constant regardless of dose
• Protein binding changes predictably with dose

Correct Answer: Small dose changes can cause disproportionate concentration changes; monitoring is essential

Q8. Which PK/PD target would you prioritize for vancomycin to predict clinical efficacy against S. aureus?

• Cmax/MIC ratio above 10
• %T>MIC greater than 50%
• AUC24/MIC of at least 400
• Minimal inhibitory concentration below 2 mg/L only

Correct Answer: AUC24/MIC of at least 400

Q9. In population PK/PD and Monte Carlo simulations, what primary output helps clinicians choose dosing regimens?

• Predicted adverse event reports per 100 patients
• Probability of target attainment (PTA) across MIC distributions
• Average protein binding values in the population
• Standardized bioavailability for all formulations

Correct Answer: Probability of target attainment (PTA) across MIC distributions

Q10. Which factor most commonly necessitates dose reduction of renally cleared drugs to avoid toxicity?

• Low protein binding
• Reduced glomerular filtration rate (GFR)
• Increased hepatic enzyme activity
• Elevated Vd due to obesity

Correct Answer: Reduced glomerular filtration rate (GFR)

Q11. What is hysteresis in PK/PD relationships?

• A rapid equilibration between plasma and effect site concentrations
• A time delay between plasma concentration changes and pharmacodynamic effect, producing a loop on concentration–effect plot
• An irreversible drug–receptor binding phenomenon leading to tolerance
• An artifact caused by poor assay sensitivity

Correct Answer: A time delay between plasma concentration changes and pharmacodynamic effect, producing a loop on concentration–effect plot

Q12. For drugs with high plasma protein binding, which change most affects free concentration and pharmacologic effect?

• A change in formulation from tablet to IV
• Displacement from binding sites by another highly protein-bound drug
• An increase in Vd due to muscle wasting
• A proportional increase in elimination half-life only

Correct Answer: Displacement from binding sites by another highly protein-bound drug

Q13. Which sampling strategy is most appropriate for routine TDM when monitoring trough concentrations for efficacy and toxicity?

• Random sampling at any time post-dose
• Peak sampling 15 minutes after infusion
• Sampling immediately before the next scheduled dose (trough)
• Sampling at exactly half the dosing interval only

Correct Answer: Sampling immediately before the next scheduled dose (trough)

Q14. A drug shows concentration-dependent killing and a significant post-antibiotic effect (PAE). Which dosing tactic is best?

• Continuous infusion to maintain low steady concentrations
• Frequent small doses to keep %T>MIC high
• Intermittent high-dose therapy to maximize Cmax and exploit PAE
• A dose reduction to avoid toxicity even if Cmax decreases

Correct Answer: Intermittent high-dose therapy to maximize Cmax and exploit PAE

Q15. When interpreting AUC-based TDM, which patient factor most directly affects AUC assuming dose unchanged?

• Bioavailability variability due to first-pass metabolism
• Change in clearance (Cl)
• Change in Vd without clearance change
• Time of day when the drug is administered

Correct Answer: Change in clearance (Cl)

Q16. Which statement best describes PK/PD breakpoint selection for an antimicrobial?

• Breakpoints are fixed values that do not consider PK variability
• Breakpoints combine MIC distributions, PK exposures achievable, and PD targets to categorize susceptibility
• Breakpoints are based solely on in vitro enzyme activity assays
• Breakpoints are identical worldwide regardless of dosing practices

Correct Answer: Breakpoints combine MIC distributions, PK exposures achievable, and PD targets to categorize susceptibility

Q17. A patient with hypoalbuminemia receives a highly protein-bound antiepileptic. What PK/PD implication is most likely?

• Total plasma concentration will rise while free concentration falls
• Free (active) concentration will increase despite lower total concentration, potentially increasing effect/toxicity
• Drug clearance will be unaffected; no dose change required
• Bioavailability will be markedly reduced

Correct Answer: Free (active) concentration will increase despite lower total concentration, potentially increasing effect/toxicity

Q18. Which method helps to individualize dosing in patients with high interindividual variability using sparse concentration data?

• Population pharmacokinetic modeling with Bayesian forecasting
• Simple linear extrapolation from average patient data
• Using fixed dose adjustments based on weight alone
• Relying solely on published mean AUC targets

Correct Answer: Population pharmacokinetic modeling with Bayesian forecasting

Q19. In PK/PD studies, the MIC is determined under standardized conditions. Which limitation should clinicians consider when applying MIC to patient therapy?

• MIC values account for host immune function and infection site penetration
• In vitro MIC does not reflect dynamic concentration changes or protein binding in vivo
• All isolates of a species have identical MICs
• MIC measurement replaces the need for PK monitoring

Correct Answer: In vitro MIC does not reflect dynamic concentration changes or protein binding in vivo

Q20. Which therapeutic scenario best illustrates the need to integrate PK/PD, TDM, and clinical context rather than relying on a single concentration value?

• Stable patient on a drug with low variability and wide therapeutic index
• Critically ill patient with augmented renal clearance receiving a time-dependent antibiotic where %T>MIC target is uncertain
• Outpatient on once-daily medication with well-established dosing
• Use of topical therapy where systemic exposure is negligible

Correct Answer: Critically ill patient with augmented renal clearance receiving a time-dependent antibiotic where %T>MIC target is uncertain

Download