Designing dosage regimens: dose and dosing interval determination MCQs With Answer

Designing Dosage Regimens: Dose and Dosing Interval Determination MCQs With Answer

This set of MCQs focuses on designing dosage regimens — calculating loading doses, maintenance doses, and choosing appropriate dosing intervals — essential skills for M.Pharm students specializing in Clinical Pharmacokinetics and Therapeutic Drug Monitoring. Questions cover core concepts such as volume of distribution, clearance, bioavailability, half-life, steady state, accumulation, infusion kinetics, and adjustments in renal or hepatic impairment. Each question tests applied understanding and formula use (for example LD = Vd·Css/F, MD = CL·Css·τ/F) and clinical reasoning for regimen selection. Practice with these items will strengthen your ability to individualize therapy and interpret pharmacokinetic parameters for safe and effective dosing.

Q1. What is the correct formula for calculating a loading dose (LD) when targeting a steady-state concentration (Css) and accounting for bioavailability (F)?

• LD = CL × Css × τ / F
• LD = Vd × Css / F
• LD = (CL × Css) / Vd
• LD = Vd × CL × Css

Correct Answer: LD = Vd × Css / F

Q2. Which expression correctly gives the maintenance dose (MD) per dosing interval τ for an orally administered drug?

• MD = Vd × Css / F
• MD = CL × Css × τ / F
• MD = CL × Css / Vd
• MD = Vd × Css × F

Correct Answer: MD = CL × Css × τ / F

Q3. For a drug given by continuous IV infusion, how is the rate of infusion (R0) to achieve a target steady-state concentration Css related to clearance (CL)?

• R0 = Vd × Css
• R0 = CL × Css
• R0 = (CL × Css) / F
• R0 = Css / CL

Correct Answer: R0 = CL × Css

Q4. A drug has a half-life of 8 hours. Approximately how many half-lives are required to reach >95% of steady state with repeated dosing?

• 1 half-life
• 3 half-lives
• 4–5 half-lives
• 10 half-lives

Correct Answer: 4–5 half-lives

Q5. Which parameter most directly determines the dosing interval (τ) when aiming to keep troughs above a minimum effective concentration?

• Volume of distribution (Vd)
• Clearance (CL)
• Elimination rate constant (ke) or half-life
• Bioavailability (F)

Correct Answer: Elimination rate constant (ke) or half-life

Q6. A 40 L volume of distribution, target plasma concentration 10 mg/L, and F = 1.0. What is the correct loading dose (LD)?

• 40 mg
• 100 mg
• 400 mg
• 4 g

Correct Answer: 400 mg

Q7. If a drug has CL = 5 L/h and the desired Css is 2 mg/L, what is the infusion rate (R0) needed to achieve Css? (Assume IV infusion.)

• 0.4 mg/h
• 2.5 mg/h
• 10 mg/h
• 0.25 mg/h

Correct Answer: 10 mg/h

Q8. Which factor must be considered when converting an IV dosing regimen to an oral regimen to maintain the same systemic exposure?

• Volume of distribution (Vd)
• Half-life (t1/2)
• Bioavailability (F)
• Protein binding

Correct Answer: Bioavailability (F)

Q9. The accumulation ratio (R) for multiple dosing at interval τ under first-order elimination is given by which expression?

• R = 1 − e^(−ke·τ)
• R = 1 / (1 − e^(−ke·τ))
• R = e^(−ke·τ)
• R = ke × τ

Correct Answer: R = 1 / (1 − e^(−ke·τ))

Q10. For drugs with concentration-dependent toxicity, which dosing strategy is generally preferred to minimize peak-related adverse effects while maintaining efficacy?

• Single large loading dose only
• Frequent smaller maintenance doses (reduce τ)
• Less frequent very large doses
• Intermittent high peaks with long intervals

Correct Answer: Frequent smaller maintenance doses (reduce τ)

Q11. When adjusting dose for a patient with reduced renal clearance, which parameter is most directly reduced and drives dose adjustment?

• Volume of distribution (Vd)
• Clearance (CL)
• Bioavailability (F)
• Absorption rate constant (ka)

Correct Answer: Clearance (CL)

Q12. Which equation indicates how to calculate dosing interval τ to maintain a specified peak-to-trough fluctuation given half-life? (Conceptual answer expected.)

• τ is chosen so that e^(−ke·τ) equals the desired trough/peak ratio
• τ = Vd / CL
• τ = CL / Vd
• τ = LD / MD

Correct Answer: τ is chosen so that e^(−ke·τ) equals the desired trough/peak ratio

Q13. A drug is 50% orally bioavailable (F = 0.5). To achieve the same systemic exposure as a 200 mg IV bolus, the equivalent oral bolus should be approximately:

• 100 mg
• 200 mg
• 400 mg
• 800 mg

Correct Answer: 400 mg

Q14. For a one-compartment drug given as repeated IV boluses, steady state trough concentration depends primarily on which two parameters?

• Vd and F
• CL and τ
• ka and Vd
• Protein binding and bioavailability

Correct Answer: CL and τ

Q15. Which statement about loading doses is TRUE?

• Loading dose influences the rate at which steady state is achieved
• Loading dose increases clearance
• Loading dose rapidly achieves target concentration but does not alter elimination kinetics
• Loading dose reduces the half-life of the drug

Correct Answer: Loading dose rapidly achieves target concentration but does not alter elimination kinetics

Q16. A drug has ke = 0.1 h−1. What is the approximate half-life (t1/2)?

• 0.693 hours
• 6.93 hours
• 69.3 hours
• 1 hour

Correct Answer: 6.93 hours

Q17. If a drug’s therapeutic range is narrow and shows large interindividual clearance variability, which approach is most appropriate to ensure safe and effective therapy?

• Use population average dosing without monitoring
• Start very high dose then taper quickly
• Individualize dosing using therapeutic drug monitoring (TDM) and adjust MD
• Avoid loading doses to prevent toxicity

Correct Answer: Individualize dosing using therapeutic drug monitoring (TDM) and adjust MD

Q18. When calculating maintenance dose for an oral drug, which adjustment ensures the desired systemic exposure is achieved?

• Divide by bioavailability (F) because oral absorption reduces delivered dose
• Multiply by volume of distribution (Vd)
• Ignore clearance because steady state depends only on Vd
• Use half the intravenous maintenance dose regardless of F

Correct Answer: Divide by bioavailability (F) because oral absorption reduces delivered dose

Q19. For a drug with first-order elimination, which change increases the average steady-state concentration for a given dosing rate?

• Increase clearance (CL)
• Decrease bioavailability (F)
• Decrease clearance (CL)
• Decrease dosing rate

Correct Answer: Decrease clearance (CL)

Q20. Which practical principle should guide the choice of dosing interval for chronically administered drugs?

• Select τ so that peak concentrations are far above the toxic threshold
• Select τ based only on convenience, ignoring PK
• Select τ to balance maintaining efficacy (above MEC) and minimizing toxicity (below MTC), considering half-life and adherence
• Always dose once daily regardless of half-life

Correct Answer: Select τ to balance maintaining efficacy (above MEC) and minimizing toxicity (below MTC), considering half-life and adherence

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