Differential effects of morning or evening dosing of amlodipine on circadian blood pressure and heart rate

Objectives: To compare the effects of morning and evening dosing of amlodipine on both circadian blood pressure (BP) and heart rate (HR) in mild-to-moderate essential hypertension. Design: A perspective, double-blind, randomized, crossover design with dose titration. Patients and methods: Sixty-two patients recruited in the study were aged 21-77 years and had mild-to-moderate essential hypertension. At the end of a 2-week single-blind, placebo run-in period, eligible patients were randomly assigned to morning (7 AM) and evening (9 PM) amlodipine treatment. The initial dose was 5 mg. After 2 weeks of double-blind therapy, patients with a seated diastolic blood pressure greater than or equal to90 mm Hg had their doses titrated upward to 10 mg, while the other patients remained on their original 5 mg doses for another 4 weeks period, than crossover to the alternate dosing regimen for 6 additional weeks. The 24-h ambulatory monitoring was performed at baseline and at 6 and 12 weeks after randomization. Results: 24- h diastolic BP load (11.0+/-17.5% vs. 6.5+/-9.1%, P<0.05) and night-time BP load (28.5 +/- 31.4%/17.7 +/- 28.2% vs. 20.0 +/- 27.9%/9.2 +/- 17.8%, P<0.05/0.05) were significantly greater with evening dosing compared with morning dosing. Nocturnal fall of BP was greater with morning dosing than with evening dosing (9.8+/-6.7/7.4+/-5.3 vs. 6.7+/-6.6/5.4+/-5.4 mm Hg, P<0.01/0.05). Percentage of nocturnal BP fall was greater with morning dosing versus with evening dosing (7.9 +/- 5.3%/9.6 +/- 6.8% vs. 5.4 +/- 7.0%/7.0 +/- 6.9%, P<0.01/0.05). Conclusions: Morning administered amlodipine had a better effect on the circadian BP compared with evening administrated amlodipine in mild-to-moderate essential hypertension.