If a drug's clearance scales with weight^0.75, how would clearance change if weight doubles?

• A. It would increase by about 1.68 (2^0.75).
• B. It would double.
• C. It would stay the same.
• D. It would decrease.

Answer: (A)

Allometric scaling often uses clearance proportional to weight to the 0.75 power. If weight doubles, the clearance multiplies by 2^0.75. Calculating 2^0.75 gives about 1.68 (since e^(0.75 × ln 2) ≈ e^0.5198 ≈ 1.68). So clearance increases by roughly 68%, not by a full double. This reflects that the relationship is positive but sublinear: increasing weight raises clearance, but less than proportionally to weight.