Prazosin in the treatment of patients with hypertension and renal functional impairment.

Prazosin was used as an additional antihypertensive agent for treating 38 patients with hypertension and renal functional impairment. The drug was effective in 29 of these patients at a mean daily dose of 7 mg. The mean blood pressure fall in these 29 patients was 28/22 mm Hg. The most frequent (10 patients) and important side effect of prazosin treatment was dizziness, which occurred on standing of after exertion and was seen either after the first dose or after a large dose increase. The "first-dose phenomenon" was a result of severe postural hypotension and was eliminated by using a starting dose of 0-5 mg every 12 hours, with the first dose being given before retiring to bed. Dosage increments were limited to 0-5 mg, beginning late in the evening. Eleven patients had a significant improvement in renal function, while a further eight patients had stable renal function. In no patient was there a deterioration in renal function which could be attributed to prazosin.