Intradermal Minoxidil Injections for the Treatment of Androgenetic Alopecia in Women

The efficacy of intradermal injections with 0.5% minoxidil for the treatment of female androgenetic alopecia (FAGA) was supported by study data published in Dermatologic Therapy. Compared with women who received placebo injections, those treated with minoxidil displayed significant improvements in hair loss and volume. Adverse events were minimal and resolved with time.

This randomized, placebo-controlled trial enrolled adult women with FAGA who received care at a private dermatology clinic in Brazil from 2012 to 2013. Patients were randomly assigned to 1 of 2 treatment groups: intradermal injections of 0.5% minoxidil or intradermal injections of 0.9% saline. Intradermal injections were administered to the affected area(s) of the scalp every week for 10 consecutive weeks. Treatment response was evaluated 6 weeks after completion of the last injection. At both the baseline and post-treatment visits, biopsy was used to determine the terminal-to-vellus hair (T:V) ratio. The percentage of anagen and telogen hairs in a sample of 50 hairs was measured using a trichogram. Patients also completed a questionnaire that asked them to self-assess changes in hair growth.

A total of 50 patients completed the study: 24 in the placebo group and 26 in the minoxidil group. Demographic characteristics were similar in treatment groups. The minoxidil group displayed a significant increase in mean T:V ratio from baseline to post-treatment (2.6 to 3.8). By contrast, T:V ratio decreased in the placebo group (2.4 to 1.7) (P <.001). The minoxidil group also displayed a significant increase in the percentage of anagen hairs, from 69.9% ±1.9% to 78.5% ± 2.0%. No change was observed in the placebo group (P =.048).

When asked to evaluate treatment results, 69.2% of patients in the minoxidil group reported a perceived improvement in hair loss, compared with 37.5% of the placebo group (P =.006). In addition, 25% of patients in the placebo group reported a worsening of hair volume. None of the participants in the minoxidil group reported worsening symptoms. When asked to rate treatment tolerability, all patients reported at least some degree of pain on the scalp. Pain levels appeared to be more severe in the minoxidil group (P <.010). No cases of hypertrichosis or injection site infection were recorded.

Study limitations include the small cohort size and short follow-up period; further study in a prospective cohort is necessary to confirm these findings, it was noted.

Results from this study support the feasibility and efficacy of 0.5% minoxidil injections for the treatment of FAGA, the researchers believe. Compared with placebo, minoxidil was associated with significant improvements in hair volume and hair loss. Minoxidil injections were generally well tolerated, with injection site pain most frequently reported.

“[B]roader studies and the standardization of the intradermal injection technique may contribute to confirmation of our results, thereby enhancing the credibility of this treatment in the specialized medical field and establishing protocols for results maintenance,” the investigators concluded.

Reference

Uzel BPC, Takano GHS, Chartuni JCN, et al. Intradermal injections with 0.5% minoxidil for the treatment of female androgenetic alopecia: a randomized, placebo-controlled trial [published online December 2, 2020]. Dermatol Ther. doi: 10.1111/dth.14622