Renal haemodynamic effects of bunazosin retard and prazosin in mild to moderately hypertensive patients with normal or moderately impaired renal function.

Effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) were measured in 53 hypertensive patients (26 renally impaired, 27 with normal renal function) before and after treatment with sufficient bunazosin retard or prazosin to control their high blood pressure. After a 3-week placebo run-in period, patients were classified as normal (creatinine clearance > 80 ml/min) or renally impaired (20-55 ml/min), and randomly assigned to bunazosin retard or prazosin. There followed a dose titration (T) phase of 6-7 weeks, and a maintenance (M) phase of 4 weeks. Blood pressure was satisfactorily controlled (sitting diastolic pressure < or = 90 mmHg or decreased by > or = 10 mmHg) by both drugs in both groups. Bunazosin Retard was associated with increases in GFR and ERPF in both normal and renally impaired groups; the increases were statistically significant in the renally impaired group (n = 14). Prazosin was associated with small decreases in both measures in both groups. One patient died of myocardial infarction during the placebo run-in. There were no other serious adverse events. Four patients reported dizziness (2 with each drug). We conclude that with appropriate dose titration, bunazosin retard is well tolerated and preserves renal blood flow when used to treat hypertension in patients with renal insufficiency.