Minoxidil

Because of the potential for serious adverse effects, minoxidil tablets are indicated only in the treatment of hypertension that is symptomatic or associated with target organ damage and is not manageable with maximum therapeutic doses of a diuretic plus two other antihypertensive drugs. At the present time use in milder degrees of hypertension is not recommended because the benefit-risk relationship in such patients has not been defined.

Minoxidil reduced supine diastolic blood pressure by 20 mm Hg or to 90 mm Hg or less in approximately 75% of patients, most of whom had hypertension that could not be controlled by other drugs.

Minoxidil tablets are contraindicated in pheochromocytoma, because it may stimulate secretion of catecholamines from the tumor through its antihypertensive action. Minoxidil is contraindicated in those patients with a history of hypersensitivity to any of the components of the preparation.

1. Salt and Water Retention Congestive Heart Failure—concomitant use of an adequate diuretic is required—Minoxidil tablets must usually be administered concomitantly with a diuretic adequate to prevent fluid retention and possible congestive heart failure; a high ceiling (loop) diuretic is almost always required. Body weight should be monitored closely. If minoxidil is used without a diuretic, retention of several hundred milliequivalents of salt and corresponding volumes of water can occur within a few days, leading to increased plasma and interstitial fluid volume and local or generalized edema.

Diuretic treatment alone, or in combination with restricted salt intake, will usually minimize fluid retention, although reversible edema did develop in approximately 10% of nondialysis patients so treated. Ascites has also been reported. Diuretic effectiveness was limited mostly by disease-related impaired renal function. The condition of patients with pre-existing congestive heart failure occasionally deteriorated in association with fluid retention although because of the fall in blood pressure (reduction of afterload), more than twice as many improved than worsened.

Rarely, refractory fluid retention may require discontinuation of minoxidil. Provided that the patient is under close medical supervision, it may be possible to resolve refractory salt retention by discontinuing minoxidil for 1 or 2 days and then resuming treatment in conjunction with vigorous diuretic therapy. 2. Concomitant Treatment to Prevent Tachycardia is Usually Required Minoxidil increases the heart rate. Angina may worsen or appear for the first time during minoxidil treatment, probably because of the increased oxygen demands associated with increased heart rate and cardiac output.