“…However, other investigators have reported achiral chlorpheniramine t 1/2 values ranging from 12 to 43 h. 6,7 Variation in chlorpheniramine t 1/2 has been attributed to variable renal elimination, which is dependent upon urinary pH and flow rate. [8][9][10][11] We therefore designed this study to minimize variation in urinary pH and flow rate by controlling diet, fluid intake, and physical activity. As a result of these controls, urinary recovery of achiral chlorpheniramine was approximately 7% of the dose, and very reproducible between subjects, as well as periods, given the lack of a ranitidine treatment effect.…”