Minoxidil is a powerful vasodilator, the pattern of action resembling hydralazine, i.e. direct relaxation of arteriolar smooth muscle with little effect on venous capacitance. Marked vasodilatation elicits strong compensatory reflexes: increased renin release and proximal tubular Na’ reabsorption — marked Na and water retention — oedema and CHF may occur; increased sympathetic activity – palpitation, increased c.o. To offset these, it has to be used along with a loop diuretic and a beta blocker.

Minoxidil is a prodrug—converted to a metabolite (by sulfate conjugation) which is an opener of ATP operated K channels; acts by hyperpolarizing smooth muscle.

Minoxidil is indicated only rarely in severe or threatening hypertension.

Minoxidil in alopecia

Oral minoxidil increases growth of body hair. Applied topically (2% twice daily it promotes hair growth in male pattern baldness. and alopecia areata. The response is slow (takes 2- 6 months) and incomplete, but up to 60% subjects derive some benefit, albeit for short periods. Baldness recurs when therapy is discontinued.

The mechanism of increased hair growth is not known; may involve:

(a) Enhanced microcirculation around hair follicles.

(b) Direct stimulation of resting hair follicles.

(c) Alteration of androgen effect on genetically programmed hair follicles.

Local irritation, itching and burning sensation are frequent. Dermatological reaction and systemic side effects (headache, dizziness, palpitation occur in 1—3% cases.

Commercial preparations –


Minoxidil topical solution and metered spray – MANEXIL 5, to apply twice a day.

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