Amlodipine in hypertension: 24-hour blood pressure control, hormonal and renal effects

The purpose of the present study is to evaluate the effects of amlodipine once daily on 24-hour BP control, hormonal and renal hemodynamic parameters, in patients with essential hypertension. This study was an open non-comparative study of amlodipine 5-10 mg once daily, which consisted of two phases: a 2-week placebo run-in period and an 8-week active treatment with amlodipine. At the end of placebo phase and at the end of treatment phase, we measured ambulatory BP for 24-hour period, PRA, plasma insulin and ANP, 24-hour urinary output of catecholamines, GFR and ERPF. Thirty patients (19 men and 11 women) withamean age of 47.8 years (range of 24-65 years) were recruited into this study. After 8 weeks of amlodipine therapy, mean 24-hour BP % SD was reduced from 160.6% 15.9/103.6% 5.5 to 134.3% 12.7/81.7% 4.0 mmHg (p < 0.001) without altering the circadian pattern. No significant changes in HR was observed. After treatment, mean PRA % SD increased from 1.74% 0.56 to 1.89% 0.54 ng/ml/h, plasma ANP from 52.1% 12.6 to 54.7% 11.0 pg/ml, plasma insulin from 19.9% 4.2 to 21.0% 4.3 μU/ml, GFR from 112.1% 11.5 to 115.8% 11.6 ml/min and ERPF from 552.0% 55.8 to 595.2% 52.9 ml/min (p <0.05 to < 0.001). Urinary catecholamines did not differ significantly between the placebo and amlodipine phases. In conclusion, amlodipine once daily is an effective antihypertensive throughout 24 hours without altering the circadian variation, and has no clinically significant effect on pressor hormones nor renal function.