ACUTE CARDIOVASCULAR EFFECTS OF THE CONCURRENT ADMINISTRATION OF ENALAPRIL, PRAZOSIN OR AMLODIPINE IN HEALTHY NIGERIANS

The acute circulatory effects of the combination of prazosin 1 mg, ena lapril 10 mg or amlodipine 5 mg were evaluated and compared in a place bo controlled, randomised, double blind, latin-square, cross-over stud y in 8 normotensive healthy Nigerians. Supine and erect blood pressure were reduced by the active treatment combinations (F= 8.8, P = 0.0006 , analysis of variance). In all, the onset of blood pressure fall was within 2 h, with a peak reduction at 4-6 h and persisting for at least 12 h. The combination of converting enzyme inhibitor and alpha blocke r, however, caused a significantly greater hypotensive action than the other combinations (P < 0.05, analysis of variance). There was a mode st reflex tachycardia in the erect position on all treatments (P = 0.0 08). Cardiac autonomic reflexes or left ventricular echocardiographic indices were unaffected by the drug combinations. The haemodynamic eff ect of enalapril plus prazosin combination, which separately cause lit tle hypotensive effect in Africans, may reflect an important pharmacod ynamic interaction between alpha(1) and angiotensin II vascular recept ors. All combinations lower blood pressure and warrant further study i n Nigerian hypertensives. However, the enalapril plus prazosin combina tion caused the greatest blood pressure fall, and caution is indicated during their concurrent use, owing to enhanced first dose hypotension .