Allometric scaling in pharmacokinetics commonly uses which body size descriptor?

• A. Age.
• B. Weight.
• C. Body surface area.
• D. Height.

Answer: (B)

Allometric scaling in pharmacokinetics hinges on how physiological processes scale with body size using a power-law relationship. The body size descriptor most commonly used is weight. This is because key PK parameters, like clearance and volume of distribution, scale with mass in a predictable way (roughly with weight^0.75 for clearance and weight^1.0 for volume). Weight directly reflects metabolic capacity and organ size across individuals, making it the most reliable and practical predictor for dosing adjustments. Age and height don’t capture overall body mass or organ capacity as effectively, and body surface area, while useful in some contexts, isn’t the standard descriptor for general allometric scaling. So weight is the best choice.