Elderly (65-73 years) and young (28-34) hypertensive patients received amlodipine by i.v. infusion (2.5, 5.0, or 10.0 mg). Patients were then started on oral amlodipine 2.5 mg daily for 2 weeks, at the end of which amlodipine disposition and effect were evaluated over one 24-h dose interval. Patients were treated subsequently with amlodipine in an escalating dose protocol (maximum 10.0 mg once daily) for 12 weeks to control blood pressure. After i.v. amlodipine, clearance tended to be decreased in elderly as compared with young patients with resulting prolongation in elimination half-life (64 +/- 20 vs. 48 +/- 8 h; mean +/- SD). Maximum decrease in systolic blood pressure (SBP) after i.v. doses tended to be greater in the elderly (-34 +/- 15 vs. -23 +/- 15 mm Hg) and maximum decrease in diastolic blood pressure (DBP) was similar in the two groups (-21 +/- 10 vs. -18 +/- 7 mm Hg). SBP was significantly decreased after 14 weeks' therapy in the elderly at doses ranging from 2.5 to 10.0 mg per day (171 +/- 17 to 149 +/- 22 mm Hg; p less than 0.01). DPB was decreased both at 2 and 14 weeks' therapy in the elderly (baseline 100 +/- 7, 2 weeks 93 +/- 5, 14 weeks 90 +/- 5 mm Hg; p less than 0.01 vs. baseline).(ABSTRACT TRUNCATED AT 250 WORDS)