Calculation of maintenance dose MCQs With Answer

Introduction: This quiz set focuses on calculation of maintenance dose — an essential topic in Clinical Pharmacokinetics and Therapeutic Drug Monitoring for M.Pharm students. You will find clear conceptual and numerical questions that reinforce how maintenance dosing depends on clearance, bioavailability, dosing interval and half-life. Problems cover infusion rates, intermittent dosing formulas, conversions between half-life and elimination rate constant, accumulation factors, and practical adjustments in renal impairment or enzyme induction. Each multiple-choice question is crafted to deepen understanding of equations and their clinical application, helping you prepare for exams and real-world dose optimization for safe and effective therapy.

Q1. Which expression correctly gives the maintenance dose per dosing interval for an oral drug with first-order kinetics?

• Maintenance dose = Css × CL × tau / F
• Maintenance dose = Css × Vd
• Maintenance dose = Css / (CL × tau)
• Maintenance dose = Loading dose × F

Correct Answer: Maintenance dose = Css × CL × tau / F

Q2. For a continuous IV infusion (bioavailability = 1), the maintenance infusion rate required to achieve a target steady‑state concentration (Css) is:

• Maintenance rate = Css / CL
• Maintenance rate = Css × CL
• Maintenance rate = Css × Vd
• Maintenance rate = Css × tau

Correct Answer: Maintenance rate = Css × CL

Q3. The elimination rate constant (kel) is related to the half‑life (t1/2) by which formula?

• kel = t1/2 × 0.693
• kel = ln(2) / t1/2
• kel = t1/2 / ln(2)
• kel = e^(−t1/2)

Correct Answer: kel = ln(2) / t1/2

Q4. Approximately how many half‑lives are required for a drug to reach steady state after repeated dosing with first‑order kinetics?

• About 1 half‑life
• About 2 half‑lives
• About 4–5 half‑lives
• About 10 half‑lives

Correct Answer: About 4–5 half‑lives

Q5. Calculate the oral maintenance dose per 12‑hour interval for a drug with CL = 5 L/hr, target Css = 10 mg/L, dosing interval τ = 12 hr and bioavailability F = 0.5.

• 600 mg
• 1200 mg
• 300 mg
• 2400 mg

Correct Answer: 1200 mg

Q6. If the dosing interval (τ) is doubled but the maintenance dose per interval is not changed, what happens to the average steady‑state concentration (Css,avg)?

• Css,avg doubles
• Css,avg remains unchanged
• Css,avg is halved
• Css,avg increases fourfold

Correct Answer: Css,avg is halved

Q7. Given t1/2 = 8 hr and τ = 12 hr, what is the accumulation factor R = 1 / (1 − e^(−kel·τ)) approximately?

• 0.65
• 1.15
• 1.55
• 2.50

Correct Answer: 1.55

Q8. For an IV bolus dosing regimen with first‑order elimination, the maintenance dose given at interval τ to achieve target average steady‑state concentration is:

• Maintenance dose = Css × CL × τ
• Maintenance dose = Css × Vd
• Maintenance dose = Css / (CL × τ)
• Maintenance dose = Loading dose × e^(−kel·τ)

Correct Answer: Maintenance dose = Css × CL × τ

Q9. If the oral bioavailability (F) of a drug decreases, what must be done to the oral maintenance dose to maintain the same Css?

• Decrease the maintenance dose proportionally
• Increase the maintenance dose proportionally (inverse of F)
• Leave the dose unchanged and shorten τ
• Switch to IV dosing without changing dose

Correct Answer: Increase the maintenance dose proportionally (inverse of F)

Q10. A patient (70 kg) receives an IV maintenance regimen. CL = 0.2 L/kg/hr, target Css = 5 mg/L, τ = 8 hr, F = 1. What is the maintenance dose per 8‑hr interval?

• 280 mg
• 560 mg
• 1120 mg
• 70 mg

Correct Answer: 560 mg

Q11. Which pharmacokinetic parameter most directly influences the calculation of maintenance dose for an orally administered drug?

• Volume of distribution (Vd)
• Elimination half‑life only
• Bioavailability (F)
• Protein binding only

Correct Answer: Bioavailability (F)

Q12. Which statement correctly contrasts loading dose (LD) and maintenance dose (MD)?

• LD depends mainly on clearance; MD depends mainly on volume of distribution
• LD and MD both depend equally on clearance and Vd
• LD is primarily determined by Vd to rapidly achieve Css; MD is determined by CL to maintain Css
• LD is always equal to MD × τ

Correct Answer: LD is primarily determined by Vd to rapidly achieve Css; MD is determined by CL to maintain Css

Q13. For an IV infusion with CL = 3 L/hr and target Css = 2 mg/L, what infusion rate (mg/hr) is required?

• 1.5 mg/hr
• 6 mg/hr
• 24 mg/hr
• 144 mg/hr

Correct Answer: 6 mg/hr

Q14. The accumulation factor for intermittent dosing is given by which expression?

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

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

Q15. If a patient’s clearance is reduced by 50% due to renal impairment, how should the maintenance dosing rate be adjusted to maintain the same Css (assuming no change in bioavailability)?

• Double the maintenance dose
• Reduce the maintenance dose by 50%
• Increase dosing frequency without changing dose
• No change needed

Correct Answer: Reduce the maintenance dose by 50%

Q16. Given t1/2 = 6 hr and Vd = 40 L, what is clearance (L/hr)?

• 0.115 L/hr
• 4.62 L/hr
• 6.93 L/hr
• 240 L/hr

Correct Answer: 4.62 L/hr

Q17. Maintenance dose calculation formulas presented in most pharmacokinetics texts assume which type of elimination kinetics?

• Zero‑order kinetics
• Mixed‑order kinetics
• First‑order kinetics
• Michaelis‑Menten non‑linear kinetics

Correct Answer: First‑order kinetics

Q18. A patient on a maintenance oral regimen has Css = 8 mg/L. An inducer doubles drug clearance while dose remains unchanged. What is the new Css (all else equal)?

• 16 mg/L
• 8 mg/L
• 4 mg/L
• 2 mg/L

Correct Answer: 4 mg/L

Q19. Rearranging the maintenance dose formula, CL = (MD × F) / (Css × τ). If MD = 1200 mg every 12 hr orally with F = 0.6 and target Css = 10 mg/L, what is the clearance (L/hr)?

• 1.2 L/hr
• 6 L/hr
• 12 L/hr
• 60 L/hr

Correct Answer: 6 L/hr

Q20. When determining a maintenance dosing regimen, which plasma concentration is most relevant to control clinical effect?

• Only the peak (Cmax) irrespective of Css
• The steady‑state concentration (Css), usually considering the pharmacologically active unbound fraction
• Only the trough (Cmin) irrespective of average levels
• Plasma concentration is irrelevant for maintenance dosing

Correct Answer: The steady‑state concentration (Css), usually considering the pharmacologically active unbound fraction

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