Pharmacokinetics of Captopril in Elderly Healthy Male Volunteers

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Abstract
The pharmacokinetics of captopril were studied in 12 healthy male volunteers aged 65 to 76 years, who each received a single 100‐mg oral dose. Blood and urine samples were collected over a 24‐hour period, and assayed for unchanged captopril (CAP), S‐methyl captopril (Me‐CAP, plasma concentrations from 2 subjects only), and total captopril levels (TOT, a mixture of CAP and its dimer and mixed disulfides with endogenous thiolcontaining compounds such as glutathione and cysteine). Mean values for the maximum concentration (Cmax) were 803 and 66.3 ng/mL for CAP and Me‐CAP, respectively. Mean time to maximum concentration (tmax) was determined as 1.0, 1.4, and 1.0 for CAP, TOT, and Me‐CAP, respectively. Mean areas under the plasma concentration‐time curve (AUC) were 1,394 hr‐ng/mL (CAP, 0–8 hr) and 17,316 hr‐ng/mL (TOT, 0–24 hr). The mean estimated half‐life (t1/2) for CAP was 1.4 hr, and its renal clearance was 187 mL/hr/kg. Mean urinary excretion over 24 hr was 20.8 and 53.1 for CAP and TOT, respectively. Cmax, and AUC for CAP were 9% less and 13% greater, respectively, than in a historical control group of 18–35‐year‐old men, treated in the same clinic, by the same personnel, using the same analytic procedures, whereas the 24‐hour urinary excretion was 25% lower and eight‐hour renal clearance 36% lower in the older population. Since the values for Cmax, AUC, and t1/2 were similar in the two populations, it does not appear that the pharmacokinetics of CAP are altered markedly with age alone.