Introduction: Pediatric dose calculations based on body surface area (BSA) are essential for safe and effective drug therapy in children. This concise guide introduces B.Pharm students to core concepts: BSA formulas (Mosteller, Dubois), unit conventions (m2, cm, kg), conversion between mg/kg and mg/m2, calculation steps, rounding and adjustments for neonates, infants and obese children, and clinical applications such as chemotherapy dosing and antibiotic dosing. Emphasis is placed on accuracy, patient safety, and understanding pharmacokinetic rationale behind BSA-based dosing (metabolic rate and clearance). Mastery of these topics prepares students for real-world dosing challenges and risk minimization. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary purpose of using body surface area (BSA) for pediatric dosing?
- To normalize drug doses to body surface area (mg/m2) for more accurate dosing across ages and sizes
- To replace weight-based dosing in all adults
- To determine body mass index for nutritional assessment
- To calculate renal clearance directly
Correct Answer: To normalize drug doses to body surface area (mg/m2) for more accurate dosing across ages and sizes
Q2. Which formula represents the Mosteller equation for calculating BSA?
- BSA = sqrt((height cm × weight kg) / 3600)
- BSA = 0.007184 × weight^0.425 × height^0.725
- BSA = (height m + weight kg) / 2
- BSA = weight^0.5 × height^0.5
Correct Answer: BSA = sqrt((height cm × weight kg) / 3600)
Q3. Which constant and exponents are used in the Dubois formula for BSA?
- 0.007184 × weight^0.425 × height^0.725
- 0.024265 × weight^0.5 × height^0.5
- 0.0098 × weight^0.33 × height^0.67
- 1.73 × weight^0.425 × height^0.725
Correct Answer: 0.007184 × weight^0.425 × height^0.725
Q4. Why is BSA often preferred over simple weight-based dosing in pediatrics?
- Because BSA correlates better with metabolic mass and drug clearance than weight alone
- Because it does not require height measurement
- Because it always yields larger doses than weight-based methods
- Because it eliminates the need for laboratory monitoring
Correct Answer: Because BSA correlates better with metabolic mass and drug clearance than weight alone
Q5. What are the correct units for reporting body surface area?
- Square meters (m2)
- Square centimeters (cm2)
- Kilograms per meter (kg/m)
- Milligrams per kilogram (mg/kg)
Correct Answer: Square meters (m2)
Q6. Calculate BSA using Mosteller for a child weighing 20 kg and 110 cm tall.
- 0.78 m2 (approx)
- 1.20 m2 (approx)
- 0.45 m2 (approx)
- 0.95 m2 (approx)
Correct Answer: 0.78 m2 (approx)
Q7. If a drug is prescribed at 150 mg/m2, what is the total dose for the child in Q6 (BSA ≈ 0.78 m2)?
- 117 mg (approx)
- 78 mg (approx)
- 234 mg (approx)
- 150 mg (fixed)
Correct Answer: 117 mg (approx)
Q8. An adult chemotherapy dose is 300 mg given as a flat dose based on a 1.73 m2 standard BSA. What dose should a child with BSA 0.78 m2 receive using BSA scaling?
- 135 mg
- 300 mg
- 78 mg
- 520 mg
Correct Answer: 135 mg
Q9. When applying the Mosteller formula, what units must be used for height and weight?
- Height in centimeters and weight in kilograms
- Height in meters and weight in pounds
- Height in inches and weight in kilograms
- Height in feet and weight in pounds
Correct Answer: Height in centimeters and weight in kilograms
Q10. Calculate BSA for a child weighing 12 kg and 85 cm tall (Mosteller formula).
- 0.53 m2 (approx)
- 0.32 m2 (approx)
- 0.75 m2 (approx)
- 1.00 m2 (approx)
Correct Answer: 0.53 m2 (approx)
Q11. For a child with weight 20 kg and height 110 cm, compare dosing: 10 mg/kg vs 300 mg/m2. Which yields the higher total dose?
- BSA dosing (300 mg/m2 → 234 mg) yields a higher dose than 10 mg/kg (200 mg)
- Weight-based dosing (10 mg/kg → 200 mg) yields a higher dose than BSA dosing
- Both methods yield the same dose
- Neither method is appropriate for this child
Correct Answer: BSA dosing (300 mg/m2 → 234 mg) yields a higher dose than 10 mg/kg (200 mg)
Q12. What is the recommended practical approach to rounding calculated pediatric doses?
- Round to the nearest clinically measurable unit (e.g., nearest 0.1 mg for potent drugs or nearest whole mg), avoiding significant deviation from the calculated dose
- Always round down to avoid toxicity
- Always round up to ensure efficacy
- Never round; administer exact decimal values
Correct Answer: Round to the nearest clinically measurable unit (e.g., nearest 0.1 mg for potent drugs or nearest whole mg), avoiding significant deviation from the calculated dose
Q13. Using the Dubois formula, estimate BSA for a child of 20 kg and 110 cm (approximate result).
- 0.77 m2 (approx)
- 0.95 m2 (approx)
- 0.45 m2 (approx)
- 1.10 m2 (approx)
Correct Answer: 0.77 m2 (approx)
Q14. If a medication dose is 5 mg/m2 and a child’s BSA is 0.53 m2, what is the calculated dose before rounding?
- 2.65 mg (before rounding)
- 0.265 mg (before rounding)
- 26.5 mg (before rounding)
- 5.53 mg (before rounding)
Correct Answer: 2.65 mg (before rounding)
Q15. Expressing a dose as mg/m2 indicates what?
- Drug dose normalized to body surface area
- Drug dose normalized to body weight only
- Drug concentration in plasma
- Drug dose per organ weight
Correct Answer: Drug dose normalized to body surface area
Q16. Which patient factor does NOT directly enter the Mosteller BSA calculation?
- Age (BSA uses weight and height, not age directly)
- Weight in kg
- Height in cm
- Both weight and height
Correct Answer: Age (BSA uses weight and height, not age directly)
Q17. For chemotherapy dosing in pediatric oncology, BSA-based dosing is commonly used because it:
- Reduces interpatient variability by correlating dose with metabolic mass and clearance
- Is simpler than weight-based dosing because it ignores height
- Always prevents toxicity regardless of organ function
- Is based on age categories rather than measurements
Correct Answer: Reduces interpatient variability by correlating dose with metabolic mass and clearance
Q18. Why can weight-based dosing be less accurate in neonates compared to BSA-based dosing?
- Neonates have different body composition and organ maturity that affect drug distribution and clearance
- Neonates have very stable metabolic rates identical to older children
- Weight-based dosing is always more accurate than BSA-based dosing in neonates
- Neonates’ heights are too large to use in formulas
Correct Answer: Neonates have different body composition and organ maturity that affect drug distribution and clearance
Q19. A drug is prescribed at 100 mg/m2. For a child 14 kg and 95 cm tall, what is the dose (Mosteller)?
- ≈60.8 mg (before rounding)
- ≈140 mg (before rounding)
- ≈95 mg (before rounding)
- ≈30.4 mg (before rounding)
Correct Answer: ≈60.8 mg (before rounding)
Q20. To convert a dose expressed in mg/kg to an equivalent mg/m2 dose for a specific child, what must you do?
- Calculate the patient’s BSA from weight and height and then determine the equivalent mg/m2 dose
- Multiply mg/kg dose by 1.73 for all children
- Use weight alone; height is not required
- Divide mg/kg dose by age in years
Correct Answer: Calculate the patient’s BSA from weight and height and then determine the equivalent mg/m2 dose
Q21. Calculate BSA (Mosteller) for a neonate weighing 3 kg and 50 cm long.
- 0.20 m2 (approx)
- 0.50 m2 (approx)
- 0.03 m2 (approx)
- 1.00 m2 (approx)
Correct Answer: 0.20 m2 (approx)
Q22. What is the commonly used reference adult BSA value for scaling and comparisons?
- 1.73 m2
- 2.50 m2
- 0.50 m2
- 3.00 m2
Correct Answer: 1.73 m2
Q23. If a calculated dose is 117 mg and the available drug concentration is 2 mg/mL, what volume should be administered?
- 58.5 mL
- 23.4 mL
- 117 mL
- 2 mL
Correct Answer: 58.5 mL
Q24. BSA correlates with which pharmacokinetic parameter important for dosing?
- Metabolic rate and drug clearance
- Plasma protein binding only
- Receptor sensitivity exclusively
- Drug potency in vitro
Correct Answer: Metabolic rate and drug clearance
Q25. How does obesity typically affect BSA-based pediatric dosing if actual weight is used without adjustment?
- BSA-based dosing may overestimate the required dose in obese children
- BSA-based dosing always underestimates the dose in obesity
- Obesity has no effect on BSA calculations
- BSA automatically corrects for excess adipose tissue
Correct Answer: BSA-based dosing may overestimate the required dose in obese children
Q26. When adjusting BSA calculations for an obese child, what is a commonly recommended approach?
- Use ideal or adjusted body weight rather than actual weight to calculate BSA
- Always use actual weight without adjustment
- Exclude height and use weight alone
- Double the calculated BSA to account for fat mass
Correct Answer: Use ideal or adjusted body weight rather than actual weight to calculate BSA
Q27. A child weighs 25 kg and is 120 cm tall. Using Mosteller, what is BSA and the total dose for a drug at 6 mg/m2?
- ≈0.913 m2 and ≈5.48 mg total
- ≈1.50 m2 and ≈9.00 mg total
- ≈0.50 m2 and ≈3.00 mg total
- ≈2.00 m2 and ≈12.00 mg total
Correct Answer: ≈0.913 m2 and ≈5.48 mg total
Q28. If a child received 50 mg of a drug and has a BSA of 0.53 m2, what dose in mg/m2 did they receive?
- ≈94.34 mg/m2
- ≈26.50 mg/m2
- ≈50.00 mg/m2
- ≈0.94 mg/m2
Correct Answer: ≈94.34 mg/m2
Q29. Which BSA formula is preferred in clinical settings for its simplicity and widespread acceptance?
- Mosteller formula (simple and widely used in clinical practice)
- Complex multi-parameter pharmacokinetic model
- Weight-only formula ignoring height
- Arbitrary clinician estimation without calculation
Correct Answer: Mosteller formula (simple and widely used in clinical practice)
Q30. For safety and accuracy, when should weight and height be measured relative to administering a BSA-based pediatric dose?
- Measured on the same day or within 24 hours before dosing
- Measured any time within the last year
- Estimated visually by the clinician
- Measured only at birth and never repeated
Correct Answer: Measured on the same day or within 24 hours before dosing
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.
Mail- Sachin@pharmacyfreak.com