Introduction: Calculation of loading dose and maintenance dose is essential for safe and effective pharmacotherapy. This introduction helps B.Pharm students understand key concepts—loading dose, maintenance dose, volume of distribution (Vd), clearance (CL), bioavailability (F), half‑life (t1/2), steady state and infusion rate—used to design dosing regimens. Practical formulas (LD = Css × Vd / F; MD = Css × CL / F) and unit conversions are emphasized to solve clinical problems for IV and oral routes, weight‑based dosing, and dose adjustments in renal or hepatic impairment. Clear, applied examples build competence in therapeutic drug monitoring and rational dosing. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which formula correctly represents the loading dose (LD) for achieving a target steady‑state concentration (Css) when bioavailability (F) is considered?
- LD = Css × CL / F
- LD = Css × Vd × F
- LD = (Css × Vd) / F
- LD = (Css × CL) / Vd
Correct Answer: (Css × Vd) / F
Q2. Which expression gives the maintenance infusion rate (MD rate) required to maintain target concentration Css for an IV infusion?
- MD rate = Vd × Css
- MD rate = CL × Css
- MD rate = Css / t1/2
- MD rate = (Css × Vd) / F
Correct Answer: CL × Css
Q3. For an oral drug with F = 0.5, Vd = 30 L, target Css = 4 mg/L, what is the loading dose?
- 240 mg
- 120 mg
- 60 mg
- 480 mg
Correct Answer: 240 mg
Q4. Which parameter primarily determines the time to reach steady state after starting a maintenance infusion?
- Volume of distribution (Vd)
- Bioavailability (F)
- Clearance (CL) via half‑life
- Loading dose value
Correct Answer: Clearance (CL) via half‑life
Q5. A drug has CL = 5 L/h and desired Css = 2 mg/L; what is the maintenance infusion rate (IV) in mg/h?
- 2.5 mg/h
- 10 mg/h
- 0.4 mg/h
- 7 mg/h
Correct Answer: 10 mg/h
Q6. Which change would increase the required loading dose to reach the same plasma concentration?
- Decrease in Vd
- Increase in Vd
- Increase in clearance
- Increase in bioavailability
Correct Answer: Increase in Vd
Q7. For oral dosing, how is maintenance dose rate adjusted compared with IV infusion?
- Multiply IV rate by F
- Divide IV rate by F
- Multiply IV rate by Vd
- No adjustment needed
Correct Answer: Divide IV rate by F
Q8. Which equation relates clearance (CL), volume of distribution (Vd), and half‑life (t1/2)?
- t1/2 = (0.693 × Vd) / CL
- t1/2 = CL / (0.693 × Vd)
- CL = Vd × t1/2
- Vd = CL × t1/2 / 0.693
Correct Answer: t1/2 = (0.693 × Vd) / CL
Q9. A drug with very large Vd will most likely require which of the following for initial therapy?
- No loading dose because steady state is fast
- A larger loading dose to rapidly achieve therapeutic levels
- A smaller maintenance dose only
- Only oral dosing is appropriate
Correct Answer: A larger loading dose to rapidly achieve therapeutic levels
Q10. If bioavailability (F) is 0.25 and an IV loading dose of 200 mg achieves Css, what oral loading dose would be required to reach the same concentration?
- 50 mg
- 800 mg
- 200 mg
- 400 mg
Correct Answer: 800 mg
Q11. Which clinical situation most strongly indicates the need for a loading dose?
- Drug with short half‑life and wide therapeutic window
- Drug with long half‑life and urgent need for therapeutic effect
- Drug given only once
- Drug with high bioavailability
Correct Answer: Drug with long half‑life and urgent need for therapeutic effect
Q12. Maintenance dose (MD) expressed per dosing interval (τ) for oral dosing is best calculated by which formula?
- MDτ = (Css × CL × τ) / F
- MDτ = Css × Vd / F
- MDτ = (Css × Vd × τ) / CL
- MDτ = CL / (Css × F × τ)
Correct Answer: MDτ = (Css × CL × τ) / F
Q13. A patient weighs 70 kg. A drug’s LD is 2 mg/kg. What total loading dose should be given?
- 35 mg
- 140 mg
- 70 mg
- 200 mg
Correct Answer: 140 mg
Q14. In renal impairment, which parameter commonly decreases and therefore reduces maintenance dose requirements?
- Volume of distribution (Vd)
- Bioavailability (F)
- Clearance (CL)
- Absorption rate
Correct Answer: Clearance (CL)
Q15. Which statement about loading dose is TRUE?
- LD depends on clearance, not Vd
- LD equals maintenance dose
- LD is used to immediately achieve therapeutic concentration based on Vd
- LD should always be half the maintenance dose
Correct Answer: LD is used to immediately achieve therapeutic concentration based on Vd
Q16. If t1/2 = 8 hours, approximately how many hours are needed to reach >90% of steady state without loading dose?
- 8 hours
- 16 hours
- 32–40 hours (4–5 half‑lives)
- 80 hours
Correct Answer: 32–40 hours (4–5 half‑lives)
Q17. Which unit combination correctly describes clearance when expressed commonly in clinical calculations?
- L·kg−1
- L/h
- mg/L
- L·h
Correct Answer: L/h
Q18. A drug has Vd = 10 L and target Css = 5 mg/L. F = 1. What is the IV loading dose?
- 50 mg
- 500 mg
- 5 mg
- 0.5 mg
Correct Answer: 50 mg
Q19. For a drug with CL = 3 L/h, desired Css = 10 mg/L, τ = 8 h, and F = 0.8, what is the approximate oral maintenance dose per dosing interval?
- 300 mg
- 240 mg
- 30 mg
- 80 mg
Correct Answer: 300 mg
Q20. Therapeutic drug monitoring shows Css below target despite correct maintenance dose — the most likely cause is:
- Increased clearance (e.g., drug interaction inducing metabolism)
- Decreased volume of distribution
- Excessive bioavailability
- Too large a loading dose
Correct Answer: Increased clearance (e.g., drug interaction inducing metabolism)
Q21. When calculating loading dose using patient weight for a hydrophilic drug, which weight is most appropriate?
- Total body weight for all patients
- Lean body weight or adjusted body weight if obese
- Always use ideal body weight regardless
- Use height only
Correct Answer: Lean body weight or adjusted body weight if obese
Q22. Which of the following decreases the effective oral loading dose required to reach target plasma levels?
- Decrease in bioavailability
- Increase in first‑pass metabolism
- Increase in bioavailability
- Increase in volume of distribution
Correct Answer: Increase in bioavailability
Q23. If a drug’s clearance doubles while Vd remains unchanged, what happens to half‑life and maintenance dose?
- t1/2 doubles; MD increases
- t1/2 halves; MD increases
- t1/2 halves; MD decreases
- t1/2 unchanged; MD unchanged
Correct Answer: t1/2 halves; MD increases
Q24. Which clinical parameter is most critical when designing a maintenance dose for a drug eliminated primarily by the liver?
- Volume of distribution
- Hepatic clearance and metabolic capacity
- Drug taste
- Route of administration only
Correct Answer: Hepatic clearance and metabolic capacity
Q25. For a narrow therapeutic index drug, which dosing strategy minimizes toxicity while achieving therapeutic levels quickly?
- Skip loading dose and use high maintenance doses
- Give appropriate loading dose followed by therapeutic monitoring and adjusted maintenance dose
- Give multiple small loading doses without monitoring
- Use only oral loading doses regardless of F
Correct Answer: Give appropriate loading dose followed by therapeutic monitoring and adjusted maintenance dose
Q26. Which calculation is necessary to convert clearance from L/h to mL/min for clinical interpretation?
- Multiply by 0.001 and divide by 60
- Multiply by 1000 and divide by 60
- Multiply by 60 and divide by 1000
- No conversion needed
Correct Answer: Multiply by 1000 and divide by 60
Q27. A drug given orally shows large first‑pass metabolism. To achieve the same plasma concentration as IV, the oral maintenance dose should be:
- Lower than IV dose
- Higher than IV dose
- Equal to IV dose
- Independent of bioavailability
Correct Answer: Higher than IV dose
Q28. Which factor does NOT directly influence the magnitude of a loading dose?
- Target plasma concentration (Css)
- Volume of distribution (Vd)
- Bioavailability (F)
- Elimination half‑life (t1/2)
Correct Answer: Elimination half‑life (t1/2)
Q29. For an intermittent oral dosing regimen, desired average Css is maintained by adjusting which of the following?
- Dosing interval (τ) and dose amount based on CL and F
- Only loading dose
- Only Vd
- Patient height only
Correct Answer: Dosing interval (τ) and dose amount based on CL and F
Q30. A clinician wants to achieve a higher peak concentration rapidly but avoid prolonged high exposure. Best approach is:
- Give a large loading dose followed by appropriately reduced maintenance doses and monitor levels
- Give no loading dose and use maximal maintenance doses
- Use loading dose only and stop therapy
- Give repeated small loading doses without monitoring
Correct Answer: Give a large loading dose followed by appropriately reduced maintenance doses and monitor levels
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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