Age and the pharmacokinetics and pharmacodynamics of chronic enalapril treatment.

Enalapril clearance after single doses is reduced in the elderly. The influence of age on the pharmacokinetics and pharmacodynamics of chronic enalapril treatment was examined in six young (22 to 31 years) and six elderly (65 to 78 years) healthy subjects who took enalapril, 10 mg, daily for 8 days. The blood pressure fall was greater in the elderly even with chronic administration. Plasma angiotensin-converting enzyme inhibition was similar in both groups. Steady-state serum enalaprilat concentrations were achieved more slowly in the elderly subjects and were correspondingly higher for all subjects. Clearance/bioavailability and volume of distribution/bioavailability diminished with repeated administration. Repeated exposure also led to a reduction in sensitivity of plasma angiotensin-converting enzyme to the inhibitor. Prolonged inhibition probably induces synthesis of new angiotensin-converting enzyme.