Dose selection, calculation, and conversion methods MCQs With Answer

Introduction: Dose selection, calculation, and conversion are essential competencies for B. Pharm students involved in safe medication use. This topic covers principles of dose determination (mg/kg, mg/m2), pharmacokinetic concepts (Vd, CL, bioavailability), practical calculations (C1V1, percent to mg/mL, mL/hr, gtt/min), pediatric and geriatric adjustments, reconstitution and dilution techniques, and unit conversions (µg↔mg, mL↔% w/v). Mastery of these methods reduces dosing errors, ensures therapeutic effectiveness, and supports clinical decision-making for diverse dosage forms. Clear procedures for loading and maintenance doses, infusion rates, and rounding rules are emphasized. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which unit expresses dose based on patient weight and is commonly used for pediatric dosing?

• mg/kg
• mg/m2
• % w/v
• mL/hr

Correct Answer: mg/kg

Q2. A medication order is 10 mg/kg for a child weighing 18 kg. What is the total dose?

• 80 mg
• 180 mg
• 1.8 g
• 0.18 mg

Correct Answer: 180 mg

Q3. Which formula is the Mosteller method for calculating body surface area (BSA)?

• BSA = (height + weight)/3600
• BSA = sqrt((height(cm) × weight(kg))/3600)
• BSA = (0.007184 × height(cm)^0.725 × weight(kg)^0.425)
• BSA = weight(kg)^0.67

Correct Answer: BSA = sqrt((height(cm) × weight(kg))/3600)

Q4. A 5% (w/v) solution equals how many mg/mL?

• 0.5 mg/mL
• 5 mg/mL
• 50 mg/mL
• 500 mg/mL

Correct Answer: 50 mg/mL

Q5. Convert 20 mg/mL to % w/v.

• 0.2% w/v
• 2% w/v
• 20% w/v
• 200% w/v

Correct Answer: 2% w/v

Q6. Which equation is used for simple dilution and reconstitution problems?

• C1 + V1 = C2 + V2
• C1V1 = C2V2
• C1/C2 = V2/V1
• C1V2 = C2V1

Correct Answer: C1V1 = C2V2

Q7. You need to prepare 250 mL of a 1% solution from a 5% stock. How many mL of stock are required?

• 5 mL
• 25 mL
• 50 mL
• 125 mL

Correct Answer: 50 mL

Q8. An IV infusion orders 400 mg over 4 hours. You have a solution of 20 mg/mL. What infusion rate in mL/hr is required?

• 5 mL/hr
• 20 mL/hr
• 40 mL/hr
• 200 mL/hr

Correct Answer: 20 mL/hr

Q9. For drop-rate calculations using a set with 15 drops/mL, how many drops per minute are needed to infuse 300 mL over 3 hours?

• 25 gtt/min
• 50 gtt/min
• 75 gtt/min
• 100 gtt/min

Correct Answer: 25 gtt/min

Q10. Which pharmacokinetic parameter is used to calculate a loading dose (LD)?

• Clearance (CL)
• Bioavailability (F)
• Volume of distribution (Vd)
• Half-life (t1/2)

Correct Answer: Volume of distribution (Vd)

Q11. The loading dose formula LD = Cp × Vd / F requires which variable to express target plasma concentration?

• Cp (target plasma concentration)
• CL (clearance)
• t1/2 (half-life)
• k (elimination rate constant)

Correct Answer: Cp (target plasma concentration)

Q12. Which formula gives maintenance dose (MD) rate for steady-state concentration?

• MD = Vd × Cp / F
• MD = CL × Cp / F
• MD = t1/2 × Cp
• MD = Vd / CL

Correct Answer: MD = CL × Cp / F

Q13. Convert 250 µg to mg.

• 0.0025 mg
• 0.025 mg
• 0.25 mg
• 2.5 mg

Correct Answer: 0.25 mg

Q14. A vial contains 500 mg of powder. After reconstitution with 10 mL diluent, what is the concentration in mg/mL?

• 5 mg/mL
• 50 mg/mL
• 500 mg/mL
• 0.05 mg/mL

Correct Answer: 50 mg/mL

Q15. To convert mg to milliequivalents (mEq), which additional information is required?

• Volume of distribution
• Molecular weight and valence
• Clearance and bioavailability
• Half-life and dosing interval

Correct Answer: Molecular weight and valence

Q16. If the oral bioavailability (F) of a drug is 0.5, how would the oral maintenance dose compare to IV to achieve same Css?

• Oral dose should be half the IV dose
• Oral dose should be equal to IV dose
• Oral dose should be double the IV dose
• Route has no effect on dose

Correct Answer: Oral dose should be double the IV dose

Q17. A prescription orders 600 mg/day divided q8h (three equal doses). What is the dose per administration?

• 200 mg
• 150 mg
• 100 mg
• 300 mg

Correct Answer: 200 mg

Q18. Rounding rules: for pediatric doses requiring syringe measurements less than 1 mL, the recommended rounding precision is typically?

• Nearest 1 mL
• Nearest 0.1 mL
• Nearest 0.01 mL
• No rounding permitted

Correct Answer: Nearest 0.01 mL

Q19. Mix 100 mL of 4% solution with 100 mL of 1% solution. What is the final concentration (% w/v)?

• 1% w/v
• 2% w/v
• 2.5% w/v
• 5% w/v

Correct Answer: 2.5% w/v

Q20. To deliver 1,200 mg over 6 hours from a solution of 40 mg/mL, what infusion rate in mL/hr is required?

• 5 mL/hr
• 20 mL/hr
• 30 mL/hr
• 50 mL/hr

Correct Answer: 5 mL/hr

Q21. A medication has a recommended dose of 50 mg/m2. If a patient’s BSA is 1.8 m2, what is the dose?

• 28 mg
• 90 mg
• 50 mg
• 180 mg

Correct Answer: 90 mg

Q22. Which conversion is correct for 1% (w/v) solution?

• 1% = 1 mg/mL
• 1% = 5 mg/mL
• 1% = 10 mg/mL
• 1% = 100 mg/mL

Correct Answer: 1% = 10 mg/mL

Q23. A continuous infusion requires 500 mL to run over 4 hours. What is the rate in mL/hr?

• 50 mL/hr
• 75 mL/hr
• 125 mL/hr
• 200 mL/hr

Correct Answer: 125 mL/hr

Q24. Which step is most important when converting a calculated dose into a deliverable formulation?

• Ignoring concentration and assuming volume will be adequate
• Selecting an appropriate concentration and performing dilution/reconstitution accurately
• Rounding to the nearest gram only
• Doubling the dose to ensure therapeutic effect

Correct Answer: Selecting an appropriate concentration and performing dilution/reconstitution accurately

Q25. A medication order: 2 mg/kg IV stat for a 70 kg adult. What is the bolus dose?

• 14 mg
• 70 mg
• 140 mg
• 700 mg

Correct Answer: 140 mg

Q26. If a vial concentration is 250 mg/5 mL, how many mg are in 1 mL?

• 25 mg
• 50 mg
• 250 mg
• 1250 mg

Correct Answer: 50 mg

Q27. To prepare a final volume of 100 mL containing 100 mg of drug, what concentration in mg/mL is needed?

• 0.1 mg/mL
• 1 mg/mL
• 10 mg/mL
• 100 mg/mL

Correct Answer: 1 mg/mL

Q28. Which practice reduces dosing errors when converting between units or calculating rates?

• Performing calculations mentally without recording steps
• Using clear, stepwise calculations with unit cancellation and independent double-check
• Relying on approximate estimates only
• Ignoring manufacturer concentration labels

Correct Answer: Using clear, stepwise calculations with unit cancellation and independent double-check

Q29. A drug order: 30 mg/kg/day divided q6h. For a 60 kg patient, what is the dose per administration?

• 90 mg every 6 hours
• 300 mg every 6 hours
• 1800 mg every 6 hours
• 30 mg every 6 hours

Correct Answer: 300 mg every 6 hours

Q30. Why is knowledge of dose conversion and calculation methods crucial for a pharmacist?

• To recommend supplements without calculations
• To ensure accurate dosing, prevent medication errors, and optimize therapeutic outcomes
• To avoid communicating with prescribers
• To increase medication costs

Correct Answer: To ensure accurate dosing, prevent medication errors, and optimize therapeutic outcomes

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