The pharmacokinetics and pharmacodynamics of adinazolam: multi-ethnic comparisons

The pharmacokinetics and pharmacodynamics of adinazolam and N-demethyladinazolam (NDMAD), its major active metabolite, were compared in 39 healthy male volunteers (13 Asian, 12 Caucasian and 14 African-American). In a four-way, double-blind crossover design, subjects were administered (1) 30 mg oral adinazolam mesylate SR tablets, (2) 10 mg parenteral (i.v.) adinazolam mesylate, (3) 30 mg i.v. NDMAD and (4) placebo. Venous blood samples were collected at specific time intervals after drug administration and assayed for adinazolam and NDMAD concentrations. Sedation was rated at the time of each blood draw according to the Nurse-Rated Sedation Scale, and the digit-symbol substitution test was administered to evaluate psychomotor performance. After i.v. administration of adinazolam, Asians manifested significantly higher Cmax, larger AUC and lower CL of both adinazolam and NDMAD than their Caucasian and African-American counterparts. Likewise, after i.v. NDMAD Asians had significantly higher NDMAD Cmax and AUC than Caucasians and African-Americans. Most of these differences remained statistically significant after controlling for body surface area. With PO adinazolam, Asians also manifested substantially higher Cmax, larger AUC and lower CL for both adinazolam and NDMAD; however, with the exception of Cmax, these differences did not reach statistical significance. These results are in accordance with previous observations for ethnic-related differences in drug pharmacokinetics. In contrast, pharmacodynamic differences were not noted among the three study groups.