5% TOPICAL MINOXIDIL SOLUTION IN THE TREATMENT OF ALOPECIA ANDROGENETICA

Minoxidil, taken orally, has been used for decades in the treatment of vascular hypertension. However, it has limited use in the treatment of hypertension because of multiple side effects. The most startling and unpredicted side effect was hair growth. Almost 80% of patients on oral minoxidil will grow hair on the body. A reversal of male pattern baldness with oral minoxidil was first reported in the American medical literature by Zappacosta ⁽¹⁾ in 1980. In 1981, Fiedler-Weiss ⁽²⁾ reported on the use of topical minoxidil for the treatment of alopecia. Subsequently, many reports on the use of topical minoxidil have been published, using minoxidil concentrations of varying strengths. Studies have shown that topically applied solutions of 2% to 5% minoxidil are effective in initiating and promoting vellus hair growth and some terminal hair growth on the scalps of individuals with male pattern alopecia ⁽³⁾. Increases in hair follicle length can be demonstrated following topical treatment with minoxidil ⁽⁴⁾.

It is important to note that minoxidil-stimulated regrowth of terminal hairs is very definitely dose-dependent. In a study at the University of Illinois, using 1% and 5% topical minoxidil solutions, 42% had response to 1% minoxidil and 84% had response to 5% minoxidil. Multiple large series studies have been reported using 2% and 3% topical minoxidil solutions. The mean time to response did not appear to be dose-related and ranged from one to nine months with the mean at 2.3 months.

Even with stronger solutions of minoxidil, there are no accounts of significant systemic effects. Side effects of topical minoxidil appear to consist entirely of cutaneous reactions such as transient mild irritation or pruritis. Because minoxidil is soluble in water only to 2%, the base vehicle had to be modified to accommodate concentrations of minoxidil up to 5%. In a placebo-control clinical trial with 3857 patients, other than local dermatologic events, no individual reaction or body system side effects were increased in the minoxidil treated group as compared to the placebo group. Allergic contact dermatitis has been reported ⁽⁵⁾, but may be due to the vehicle rather than minoxidil. No major systemic side effects have been attributed to topical minoxidil therapy at any concentration.

According to the prescribing information provided by Upjohn for the use of Rogaine, an effort was made to explore the potential for systemic effects of topical minoxidil (1,2 and 5%) applied twice daily. The results were compared to oral doses (2.5 and 5 mg given once daily) and placebo. Since normotensive patients have little or no blood pressure response to minoxidil at doses of 10 mg per day, hypertensive patients were used for this double-blind controlled trial. The results showed detectable blood pressure decrease in the group taking 5 mg oral doses. No other group had a clear effect. The failure to detect evidence of systemic effects during treatment with topical minoxidil reflects the poor absorption of topically applied minoxidil, which averages about 1.4% (range 0.3 to 4.5%) from normal intact scalp. Since it requires a concentration of 20 nanograms/mL to cause even minimal hemodynamic effects in the body, there is approximately a 16 fold safety margin in the use of 5% topical minoxidil. ⁽⁶⁾

The recommended dosage is 1ml applied twice daily to the thinning areas of the scalp. As much as possible, the liquid should be directly applied to the skin to maximize the amount that will be absorbed. It is not necessary to use more than 1ml regardless of the size of the thinning or bald area. Excess fluid should be controlled by the fingertips and reapplied to the affected areas. The scalp should be dry or relatively dry. If you are using minoxidil solutions that contain retinoic acid, those solutions should only be applied at night because retinoic acid is decomposed by strong light and so becomes ineffectual when it is exposed to strong light. To achieve maximum regrowth, a 2% spironolactone solution should be applied in the nighttime a few seconds before applying the minoxidil solutions.

In summary, higher concentrations of minoxidil are more effective in promoting hair growth and do not have systemic side effects. These minoxidil solutions promote maximum regrowth when used in conjunction with a 2% spironolactone solution or other anti-androgen.

⁽¹⁾Zappacosta AR: Reversal of baldness in a patient receiving minoxidil for hypertension. N Engl J Med 303:1480-1481, 1980

⁽²⁾Olsen EA, Weiner MS, Delong ER, et al: Topical minoxidil in early male pattern baldness. J Am Acad Dermatol 82:90-93, 1984

⁽³⁾Weiss VC, West DP, Mueller CE: Topical minoxidil in alopecia areata. J Am Acad Dermatol 5:224-226, 1981

⁽⁴⁾Weiss VC, Uno H, Buys CM, et al: Histologic and immunopathic profiles in alopecia totalis patients receiving topical minoxidil (1% and 5%). J Invest Dermatol 84:360, 1985

⁽⁵⁾Tosti A, Bardazzi F, DePadova MP, et al: Contact dermatitis due to minoxidil. Contact Derm 13:275-276, 1985

⁽⁶⁾Whiting, David A.:Clinical Studies with Finasteride in men with Androgenetic Alopecia, presented 14 Feb. 1998: New Therapeutic Approaches to Alopecia

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