Introduction to pharmacokinetics and toxicokinetics MCQs With Answer

Introduction:

This quiz collection titled Introduction to Pharmacokinetics and Toxicokinetics MCQs With Answer is designed for M.Pharm students studying Modern Bio-Analytical Techniques (MPA 202T). The set focuses on core PK/TK concepts — absorption, distribution, metabolism, excretion, compartmental models, clearance, volume of distribution, half-life, bioavailability, and toxicokinetic dose metrics — and links these concepts to bioanalytical considerations such as sampling matrix, assay sensitivity and unbound drug measurements. Each question challenges conceptual understanding and practical interpretation of PK/TK data commonly encountered in preclinical and clinical bioanalysis, helping students prepare for exams and applied laboratory work.

Q1. Which statement best defines pharmacokinetics?

• The study of drug effects and mechanisms at target receptors
• The quantitative study of drug absorption, distribution, metabolism and excretion over time
• The assessment of adverse drug reactions in populations
• The design of dosage forms to improve patient adherence

Correct Answer: The quantitative study of drug absorption, distribution, metabolism and excretion over time

Q2. Absolute bioavailability (F) is most directly estimated by which ratio?

• AUCpo / AUCiv
• (AUCpo × Doseiv) / (AUCiv × Dosepo)
• Cmax_po / Cmax_iv
• (Tmax_po) / (Tmax_iv)

Correct Answer: (AUCpo × Doseiv) / (AUCiv × Dosepo)

Q3. Volume of distribution (Vd) primarily indicates:

• The total amount of drug eliminated per unit time
• The theoretical volume required to contain the total drug amount at the measured plasma concentration
• The fraction of drug bound to plasma proteins
• The bioavailability after oral dosing

Correct Answer: The theoretical volume required to contain the total drug amount at the measured plasma concentration

Q4. Clearance (CL) is best described as:

• The half-life multiplied by the volume of distribution
• The volume of plasma from which the drug is completely removed per unit time
• The fraction of drug absorbed from the gastrointestinal tract
• The maximum rate of drug metabolism under saturation

Correct Answer: The volume of plasma from which the drug is completely removed per unit time

Q5. The elimination half-life (t1/2) in a one-compartment linear system is related to clearance and volume of distribution by which expression?

• t1/2 = CL / (0.693 × V)
• t1/2 = 0.693 × V / CL
• t1/2 = V × CL
• t1/2 = 1 / (CL × V)

Correct Answer: t1/2 = 0.693 × V / CL

Q6. A fundamental assumption of a one-compartment model is:

• The body consists of two kinetically distinct compartments with rapid equilibrium
• The drug distributes instantaneously and uniformly throughout a single, well-mixed compartment
• Elimination occurs only from a peripheral compartment
• Absorption rate is always slower than elimination rate

Correct Answer: The drug distributes instantaneously and uniformly throughout a single, well-mixed compartment

Q7. Nonlinear pharmacokinetics often results from which mechanism?

• First-order renal clearance independent of dose
• Capacity-limited metabolism described by Michaelis–Menten kinetics
• Instantaneous and unlimited tissue binding
• Complete and constant oral bioavailability

Correct Answer: Capacity-limited metabolism described by Michaelis–Menten kinetics

Q8. Hepatic extraction ratio (EH) is defined as:

• EH = Ce / Ca where Ce is hepatic effluent concentration
• EH = (Ca – Cv) / Ca where Ca is arterial and Cv is hepatic venous concentration
• EH = CLrenal / CLtotal
• EH = Tmax / Cmax

Correct Answer: EH = (Ca – Cv) / Ca where Ca is arterial and Cv is hepatic venous concentration

Q9. In therapeutic drug monitoring, why is measuring unbound (free) drug concentration often more informative than total drug concentration?

• Unbound concentration is less affected by sampling time
• Only unbound drug is pharmacologically active and available for clearance and tissue distribution
• Total concentration is always proportional to unbound concentration regardless of binding changes
• Unbound concentration is easier to measure analytically

Correct Answer: Only unbound drug is pharmacologically active and available for clearance and tissue distribution

Q10. After repeated dosing at fixed intervals, steady state is typically achieved after approximately how many half-lives?

• 1 half-life
• 2 half-lives
• 4–5 half-lives
• 10–12 half-lives

Correct Answer: 4–5 half-lives

Q11. Area under the plasma concentration-time curve (AUC) most directly reflects which of the following?

• Rate of absorption only
• Total systemic exposure to the drug over time
• Maximum effect at the target site
• Volume of distribution

Correct Answer: Total systemic exposure to the drug over time

Q12. Noncompartmental analysis (NCA) typically estimates pharmacokinetic parameters using which approach?

• Solving differential equations for compartment models
• Statistical moment theory and the trapezoidal rule to estimate AUC and related parameters
• Assuming infinite clearance to simplify calculations
• Relying solely on peak concentrations without time integration

Correct Answer: Statistical moment theory and the trapezoidal rule to estimate AUC and related parameters

Q13. Which sampling matrix is most commonly used for human pharmacokinetic studies to assess systemic exposure?

• Urine only
• Faeces only
• Plasma or serum
• Tissue biopsy samples from the target organ

Correct Answer: Plasma or serum

Q14. For a drug that exhibits concentration-dependent toxicity related to peak exposure, which pharmacokinetic metric is most predictive of toxicity?

• AUC over dosing interval
• Cmax
• Trough concentration (Cmin)
• Apparent volume of distribution

Correct Answer: Cmax

Q15. Which of the following statements regarding first-pass metabolism is correct?

• First-pass metabolism increases absolute bioavailability
• It refers to presystemic elimination in the gut wall and liver that can substantially reduce oral bioavailability
• It only occurs after intravenous dosing
• It is independent of hepatic blood flow and enzyme activity

Correct Answer: It refers to presystemic elimination in the gut wall and liver that can substantially reduce oral bioavailability

Q16. In linear (dose-proportional) pharmacokinetics, which parameter remains constant across different doses?

• Clearance (CL)
• Cmax/Dose ratio
• Half-life only at very high doses
• Vmax of metabolism

Correct Answer: Clearance (CL)

Q17. Which bioanalytical consideration is most critical when interpreting PK data for a highly protein-bound drug?

• Only total concentration is relevant; unbound fraction can be ignored
• Measurement of unbound concentration or accurate determination of unbound fraction to relate measured concentrations to pharmacologic effect
• Assume unbound fraction is constant across disease states and drug interactions
• Tissue binding replaces the need to assess plasma protein binding

Correct Answer: Measurement of unbound concentration or accurate determination of unbound fraction to relate measured concentrations to pharmacologic effect

Q18. Which statement correctly describes toxicokinetics (TK) in safety assessment?

• Toxicokinetics ignores dose–exposure relationships and focuses only on clinical signs
• TK characterizes internal exposure (e.g., AUC, Cmax) after toxicology dosing to link dose to systemic exposure and potential toxicity
• Toxicokinetics only applies to inhalation exposures
• Toxicokinetics replaces the need for pharmacodynamic evaluation in toxicology studies

Correct Answer: TK characterizes internal exposure (e.g., AUC, Cmax) after toxicology dosing to link dose to systemic exposure and potential toxicity

Q19. Which dosing strategy will increase accumulation of a drug between doses?

• Using a dosing interval much longer than the elimination half-life
• Shortening the dosing interval relative to the elimination half-life
• Decreasing the dose while keeping the same interval
• Switching from oral to intravenous administration without changing dose or interval

Correct Answer: Shortening the dosing interval relative to the elimination half-life

Q20. Advantages of microsampling techniques (e.g., dried blood spots, capillary microsampling) in PK/TK studies include:

• Increased blood volume requirement and reduced sampling frequency
• Lower assay sensitivity and greater matrix effects compared with large-volume plasma samples
• Reduced animal and patient blood loss, enabling richer time profiles and serial sampling in small subjects
• Elimination of the need for method validation

Correct Answer: Reduced animal and patient blood loss, enabling richer time profiles and serial sampling in small subjects

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