Description

Minoxidil, also known as 2,4-diamino-6-piperidinopyrimidine3-n-oxide, is an organic compound with the chemical formula C₉H₁₅N₅O. This compound is slightly soluble in water, soluble in methanol, and in propylene glycol. As a useful medicine, minoxidil acts through multiple pathways (vasodilator, anti-inflammatory agent, inducer of the Wnt/β-catenin signaling pathway, and antiandrogen), and may also affect the length of the anagen and telogen phases.

History

This drug was initially developed in the 1970s as a potent peripheral vasodilator agent for the treatment of severe refractory hypertension. Minoxidil exerts its antihypertensive effect by opening adenosine triphosphate (ATP)-sensitive potassium channels, thereby reducing peripheral resistance and lowering blood pressure levels in patients. However, owing to the significant adverse effects of taking oral minoxidil, this drug is currently used only for patients with resistant hypertension who do not adequately respond to the maximum doses of 3 different classes of antihypertensive medications[1]. In 1987, a topical formulation of minoxidil was developed to treat androgenic alopecia, initially targeting males and later expanding its use to include females.

Uses

Topical minoxidil (5% foam, 5% solution, and 2% solution) is FDA-approved for androgenetic alopecia (AGA) in men and women. Approximately 1.4% of topical minoxidil is absorbed through the skin. Minoxidil is a prodrug that is metabolized by follicular sulfotransferase to minoxidil sulfate (active form). Those with higher sulfotransferase activity may respond better than patients with lower sulfotransferase activity. In a five-year study that researched the clinical efficacy of topical minoxidil, 2% minoxidil exhibited peak hair growth in males at year one with a decline in subsequent years. Topical minoxidil causes hair regrowth in both frontotemporal and vertex areas[2-3]. The 5% solution and foam were not significantly different in efficacy from the 2% solution.

Minoxidil, when used for hypertension, is generally reserved for use in severe hypertension patients who can not respond to at least two agents and a diuretic. Minoxidil is also generally administered with a loop diuretic to prevent sodium and potassium retention. It may also cause reflex tachycardia and thus is prescribed with a beta blocker.

References

[1] Jimenez-Cauhe J, et al. Effectiveness and safety of low-dose oral minoxidil in male androgenetic alopecia. J Am Acad Dermatol, 2019; 81: 648-649.

[2] Gupta A, et al. Minoxidil: a comprehensive review. Journal of Dermatological Treatment, 2021; 33: 1896-1906.

[3] Goren A, et al. Minoxidil in the treatment of androgenetic alopecia. Dermatologic Therapy, 2018; 31: e12686.