AMLODIPINE, A LONG-ACTING CALCIUM CHANNEL BLOCKER, ATTENUATES MORNING BLOOD PRESSURE RISE IN HYPERTENSIVE PATIENTS

ABSTRACT

1. The effects of once-daily calcium channel blockers with different plasma half-lives on diurnal blood pressure changes were examined in hypertensive patients.

2. Patients with essential hypertension, nine men and 13 women aged 61±2 years, were treated with amlodipine or nitrendipine in a random cross-over design for 12–16 weeks each. The study drugs were given once daily as monotherapy (n = 8) or in combination with other classes of antihypertensive drugs (n = 14). The plasma half-life of amlodipine is as long as 36 h, while that of nitrendipine is 10 h. At the end of each treatment period, 24 h ambulatory blood pressure and pulse rate were monitored.

3. Average office blood pressure was comparably controlled below 140/90 mmHg by either amlodipine or nitrendipine, both in the monotherapy and the combination therapy groups; however, pulse rate was greater in nitrendipine than in amlodipine either in the monotherapy (by 6 b.p.m., P < 0.05) or in the combination therapy (by 5 b.p.m., P < 0.01).

4. In 24 h blood pressure monitoring, morning (05.30–09.00 h) blood pressure was higher in nitrendipine than in amlodipine by 6/4 mmHg in the monotherapy (P < 0.05) and by 7/5 mmHg in the combination therapy (P < 0.03), although the blood pressure in the remainder of the 24 h did not differ between the two treatment periods. In addition, pulse rate in the daytime (09.30–18.00 h) was greater in nitrendipine than in amlodipine by 6 b.p.m. in the monotherapy (P < 0.01) and by 7 b.p.m. in the combination therapy (P < 0.02).

5. These results suggest slow pharmacokinetics of amlodipine provides an advantage in controlling morning blood pressure and mitigating reflex activation of the sympathetic nervous system.