A research participant of average male sex has higher gastric ADH activity than an average female. If both drink the same dose fasted, which immediate pharmacokinetic change would you analyze to quantify the effect of gastric ADH on BAC?

• A. Assess hair ethanol content because gastric ADH alters the rate of ethanol incorporation into keratin as a direct readout of pre-systemic metabolism.
• B. Compare the early area under the BAC-time curve (AUC) in the first hour and the proportion of dose absorbed (inferred from peak BAC), since pre-systemic gastric metabolism reduces early systemic exposure.
• C. Measure acetaldehyde levels in urine 48 hours later because gastric ADH directly changes long-term excretion patterns rather than immediate blood concentrations.
• D. Compare carbon dioxide production as a surrogate for ethanol conversion to acetate, since gastric ADH primarily drives whole-body CO2 output following intake.

Answer: (B)