Drug Groups

approved

Description

A potent direct-acting peripheral vasodilator (vasodilator agents) that reduces peripheral resistance and produces a fall in blood pressure. (From Martindale, The Extra Pharmacopoeia, 30th ed, p371)

Indication

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.

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.

Affected Organisms

Biotransformation

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.

Absorption

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

Half Life

4.2 hours

Protein Binding

Minoxidil does not bind to plasma proteins.

References

External Links