Clinically additive effect between doxazosin and amlodipine in the treatment of essential hypertension

The Joint National Committee on Prevention, Detection, Evaluation, and Trea tment of High Blood Pressure has reported that combinations of low doses of antihypertensive agents from different classes may provide additional anti hypertensive efficacy and minimize the likelihood of dose-dependent adverse effects. Doxazosin and amlodipine, alone and in combination, were compared for efficacy in reducing blood pressure (BP) in 75 patients with predomina ntly moderate (Stage 2) hypertension. This was a double-blind, randomized, crossover study. After a 2-week washou t period, patients in group A (n = 37) received amlodipine 10 mg and patien ts in group B (n = 38) received doxazosin 4 mg for 6 weeks. All patients th en received reduced-dose combination therapy (amlodipine 5 mg and doxazosin 2 mg) for 6 weeks. Subsequently, patients received 6 weeks of monotherapy with the alternate m edication (group A received doxazosin 4 mg and group B received amlodipine 10 mg). During both monotherapy periods, doxazosin and amlodipine significantly red uced systolic and diastolic BP (P < .001 v baseline). BP further decreased with combination therapy (P < .01 v monotherapy). The percentage of patient s with Stage 2 hypertension who achieved a target BP of < 140/ < 90 mm Hg i ncreased from 78% with monotherapy to 94% with combination therapy. Fewer a dverse effects were observed during combination therapy. It is concluded that there is an additional fall in blood pressure when red uced doses of doxazosin and amlodipine are used in combination for the trea tment of hypertension, suggesting that doxazosin should be considered as an effective add-on treatment to calcium-channel blockers. (C) 2000 American Journal of Hypertension, Ltd.