Overview
DESCRIPTION Minoxidil tablets contain minoxidil, an antihypertensive peripheral vasodilator. Minoxidil occurs as a white to off-white, crystalline powder, soluble in alcohol and propylene glycol; sparingly soluble in methanol; slightly soluble in water; practically insoluble in chloroform, acetone and ethyl acetate.
Mechanism of Action
CLINICAL PHARMACOLOGY 1. General Pharmacologic Properties Minoxidil is an orally effective direct acting peripheral vasodilator that reduces elevated systolic and diastolic blood pressure by decreasing peripheral vascular resistance. Microcirculatory blood flow in animals is enhanced or maintained in all systemic vascular beds. In man, forearm and renal vascular resistance decline; forearm blood flow increases while renal blood flow and glomerular filtration rate are preserved. Because it causes peripheral vasodilation, minoxidil elicits a number of predictable reactions.
Indications
- INDICATIONS AND USAGE 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.
Common Doses
- 5 mg
- 40 mg
- 100 mg
- 0.2 mg
Dosage
DOSAGE AND ADMINISTRATION Patients over 12 years of age: The recommended initial dosage of minoxidil tablets is 5 mg of minoxidil given as a single daily dose. Daily dosage can be increased to 10, 20 and then to 40 mg in single or divided doses if required for optimum blood pressure control. The effective dosage range is usually 10 to 40 mg per day. The maximum recommended dosage is 100 mg per day. Patients under 12 years of age: The initial dosage is 0.2 mg/kg minoxidil as a single daily dose.
Black Box Warning
WARNING Minoxidil tablets contain the powerful antihypertensive agent, minoxidil, which may produce serious adverse effects. It can cause pericardial effusion, occasionally progressing to tamponade, and angina pectoris may be exacerbated. Minoxidil should be reserved for hypertensive patients who do not respond adequately to maximum therapeutic doses of a diuretic and two other antihypertensive agents. In experimental animals, minoxidil caused several kinds of myocardial lesions as well as other adverse cardiac effects (see Cardiac Lesions in Animals ).
Contraindications
- CONTRAINDICATIONS Minoxidil tablets are contraindicated in pheochromocytoma, because it may stimulate secretion of catecholamines from the tumor through its antihypertensive action. Minoxidil tablets are contraindicated in those patients with a history of hypersensitivity to any of the components of the preparation.
Side Effects
- ADVERSE REACTIONS 1. Salt and Water Retention (see WARNINGS: Concomitant use of Adequate Diuretic is Required ) — Temporary edema developed in 7% of patients who were not edematous at the start of therapy. 2. Pericarditis, Pericardial Effusion and Tamponade (see WARNINGS ). 3. Dermatologic — Hypertrichosis — Elongation, thickening, and enhanced pigmentation of fine body hair are seen in about 80% of patients taking minoxidil tablets. This develops within 3 to 6 weeks after starting therapy.
Interactions
- 4. Drug interactions See " Interaction with Guanethidine " under WARNINGS .