The effect of the new
vasodilator,
minoxidil, on blood pressure and plasma
renin activity was studied in 21 hypertensive patients: 12 patients with essential and 9 with
renal hypertension. The average maximum dosage of
minoxidil was 27.9 +/- 6.0 mg/day (M +/- SD). Average
duration of treatment was 84.5 days. During the observation period the average systolic blood pressure fell from 195 +/- 18 to 159 +/- 7 mm Hg (M +/- SD), and the mean diastolic blood pressure fell from 120 +/- 8.3 to 92.5 +/- 8 mm Hg (p less than 0.01). These patients had been treated earlier with other
antihypertensive agents, such as
reserpine, saluretics,
hydralazine,
alpha-methyldopa, and
clonidine, without any significant reduction in blood pressure. Before treatment, plasma
renin activity after resting was 59 +/- 6.4 ng/ml/16 h (M +/- SE) and after saluretics and
orthostasis 89 +/- 12.7 ng/ml/16 h.
After treatment, the decline in
renin value after resting was statistically significant: 42.7 +/- 3.3 ng/ml/16 h (p less than 0.05), and the stimulated
renin had fallen to 70 +/- 3.4 ng/ml/16 h (p greater than 0.1). A comparison of the
renin stimulation values of patients with
renal hypertension also revealed a significant reduction (p less than 0.01). Side effects which appeared at a daily dose of 15 to 30 mg consisted mainly of
tachycardia and fluid retention and could be controlled by the administration of
propranolol and
chlorthalidone. In 5 women and in 1 man was observed a cosmetically disturbing, reversible
hypertrichosis.
Orthostatic hypotension was observed in one patient.
Minoxidil is an effective
antihypertensive agent. However, because of its side effects, it generally must be administered with beta-receptor blocking agents and saluretics. It is possible that its blood pressure lowering effect is due, at least in part, to a suppression of the plasma
renin activity.