Monotherapy: Initial dosage is 5 mg/day PO as a single dose. Daily dosage can be increased to 10, 20, then 40 mg in single or divided doses. Effective range is usually 10–40 mg/day PO. Maximum dosage is 100 mg/day. If supine diastolic BP has been reduced less than 30 mm Hg, administer the drug only once a day. If reduced more than 30 mm Hg, divide the daily dose into two equal parts. Dosage adjustment should normally be at least at 3-day intervals; in emergencies, every 6 hr with careful monitoring is possible.

Concomitant therapy with diuretics: Use minoxidil with a diuretic in patients relying on renal function for maintaining salt and water balance; the following diuretic dosages have been used when starting minoxidil therapy: Hydrochlorothiazide, 50 mg bid; chlorthalidone, 50–100 mg daily; furosemide, 40 mg bid. If excessive salt and water retention result in weight gain more than 5 lb, change diuretic therapy to furosemide; if patient already takes furosemide, increase dosage.

Concomitant therapy with beta-adrenergic blockers or other sympatholytics: The following dosages are recommended when starting minoxidil therapy: Propranolol, 80–160 mg/day; other beta blockers, dosage equivalent to the above; methyldopa 250–750 mg bid (start methyldopa at least 24 hr before minoxidil); clonidine, 0.1–0.2 mg bid.