Why is body surface area used for dosing certain drugs in pediatrics?

• A. Because body weight is the only predictor of drug pharmacokinetics.
• B. Because BSA dosing is easier than weight-based dosing.
• C. Because BSA is unrelated to dosing.
• D. Because some drugs' pharmacokinetics correlate better with body surface area than weight, providing more accurate dosing for children.

Answer: (D)

Dosing by body surface area is used for certain pediatric drugs because how a drug is absorbed, distributed, metabolized, and eliminated often aligns more closely with the body's surface area than with weight. In children, organ size, blood flow, and metabolic capacity don’t scale perfectly with weight alone, and two kids with the same weight can have different body compositions and maturational status. Body surface area tends to reflect these differences better, so BSA-based dosing aims to produce similar drug exposure across a range of ages and sizes, reducing the risk of under- or overdosing. This approach is especially important for drugs with narrow therapeutic windows or where clearance hinges on organ function. Not every drug follows this pattern, so clinicians reserve BSA dosing for those where pharmacokinetics are better predicted by body surface area.