Active ingredient: Minoxidil - Brands, Medical Use, Clinical Data

Brands, Medical Use, Clinical Data

Drug Category

• Vasodilator Agents
• Antihypertensive Agents

Dosage Forms

• Liquid
• Tablet

Brands / Synonyms

Alopexil; Alostil; Apo-Gain; Gen-Minoxidil; Loniten; Lonolox; Minodyl; Minossidile; Minossidile [Italian]; Minoxidil; Minoxidil [Usan:Ban:Inn]; Minoxidilum [Inn-Latin]; Minoxigaine; Minoximen; Normoxidil; PDP; Pierminox; Prexidil; Regaine; Rogaine; Rogaine Extra Strength for Men; Rogaine for Men; Rogaine for Women; Theroxidil; Triclosan; Tricoxidil; Trocoxidil

Indications

For the treatment of severe hypertension and in the topical treatment (regrowth) of androgenic alopecia in males and females and stabilisation of hair loss in patients with androgenic alopecia.

Pharmacology

Minoxidil is an orally effective direct acting peripheral vasodilator that reduces elevated systolic and diastolic blood pressure by decreasing peripheral vascular resistance. Minoxidil is also used topically to treat androgenetic alopecia. 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. The predominant site of minoxidil action is arterial. Venodilation does not occur with minoxidil; thus, postural hypotension is unusual with its administration. The antihypertensive activity of minoxidil is due to its sulphate metabolite, minoxidil sulfate.

Mechanism of Action

Minoxidil is thought to promote the survival of human dermal papillary cells (DPCs) or hair cells by activating both extracellular signal-regulated kinase (ERK) and Akt and by preventing cell death by increasing the ratio of BCl^-2/Bax. Minoxidil may stimulate the growth of human hairs by prolonging anagen through these proliferative and anti-apoptotic effects on DPCs. Minoxidil, when used as a vasodilator, acts by opening adenosine triphosphate-sensitive potassium channels in vascular smooth muscle cells. This vasodilation may also improve the viability of hair cells or hair follicles.

Absorption

Minoxidil is at least 90% absorbed from the GI tract in experimental animals and man.

Toxicity

Oral LD₅₀ in rats has ranged from 1321-3492 mg/kg; in mice, 2456-2648 mg/kg. Side effects include cardiovascular effects associated with hypotension such as sudden weight gain, rapid heart beat, faintness or dizziness.

Biotrnasformation / Drug Metabolism

Approximately 90% of the administered drug is metabolized, predominantly by conjugation with glucuronic acid at the N-oxide position in the pyrimidine ring, but also by conversion to more polar products. Known metabolites exert much less pharmacologic effect than minoxidil itself.

Contraindications

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.

Drug Interactions

Interaction with Guanethidine: Although minoxidil does not itself cause orthostatic hypotension, its administration to patients already receiving guanethidine can result in profound orthostatic effects. If at all possible guanethidine should be discontinued well before minoxidil is begun. Where this is not possible, minoxidil therapy should be started in the hospital and the patient should remain institutionalized until severe orthostatic effects are no longer present or the patient has learned to avoid activities that provoke them.