Relative Efficacy of Minoxidil and the 5-α Reductase Inhibitors in Androgenetic Alopecia Treatment of Male Patients: A Network Meta-analysis

Abstract

Importance: There are knowledge gaps regarding the relative efficacy of 3 commonly used drugs for androgenetic alopecia (AGA), namely, minoxidil and the two 5-α reductase inhibitors dutasteride and finasteride.

Objective: To examine the relative efficacy of any dose and administration route of minoxidil, dutasteride, and finasteride for the treatment of male AGA.

Data sources: Systematic searches were performed in PubMed on March 5, 2021, without date restrictions.

Study selection: Eligible studies included those that investigated monotherapy with any dose and administration route of minoxidil, dutasteride, and finasteride.

Data extraction and synthesis: Data on the mean (SD) difference and sample size were used for the bayesian network meta-analyses. League tables and surface under the cumulative ranking curve values were used to examine the relative efficacy of the interventions.

Main outcomes and measures: Study end points were change in total and terminal hair count after 24 and 48 weeks of therapy. The 4 end points were quantified in hairs per square centimeters.

Results: The PubMed search yielded 848 records; after the 2 stages of screening, 23 studies were eligible for quantitative analyses. Mean (SD) age of patients ranged from 22.8 (3.3) years to 41.8 (12.3) years. The greatest increase in total hair count at 24 weeks (ie, first end point) was with 0.5 mg/d of dutasteride, which was significantly more efficacious than 1 mg/d of finasteride (mean difference, 7.1 hairs/cm2; 95% CI, 5.1-9.3 hairs/cm2) and minoxidil (0.25 mg/d [mean difference, 23.7 hairs/cm2; 95% CI, 9.5-38.0 hairs/cm2], 5 mg/d [mean difference, 15.0 hairs/cm2; 95% CI, 3.9-26.1 hairs/cm2], and 2% solution [mean difference, 8.5 hairs/cm2; 95% CI, 4.8-12.3 hairs/cm2]). The greatest increase in terminal hair count at 24 weeks (ie, second end point) was with 5 mg/d of minoxidil, which was significantly more efficacious than the 0.25-mg/d dose (mean difference, 43.6 hairs/cm2; 95% CI, 29.7-57.7 hairs/cm2) and its topical forms (in 2% [mean difference, 29.3 hairs/cm2; 95% CI, 21.1-37.5 hairs/cm2] and 5% [mean difference, 29.8 hairs/cm2; 95% CI, 19.7-39.8 hairs/cm2]); 5 mg/d of minoxidil was significantly more efficacious than 1 mg/d of finasteride (mean difference, 10.4 hairs/cm2; 95% CI, 2.2-18.6 hairs/cm2). The greatest increase in total hair count at 48 weeks (ie, third end point) was with 5 mg/d of finasteride, which was significantly more efficacious than 2% topical minoxidil (mean difference, 20.7 hairs/cm2; 95% CI, 9.5-31.9 hairs/cm2). The greatest increase in terminal hair count at 48 weeks (ie, fourth end point) was with 1 mg/d of finasteride, which was significantly more effective than topical minoxidil (in 2% [mean difference, 32.1 hairs/cm2; 95% CI, 23.9-40.3 hairs/cm2] and 5% [mean difference, 26.2 hairs/cm2; 95% CI, 16.2-36.2 hairs/cm2]).

Conclusions and relevance: As efficacy data from head-to-head trials accumulate, there could be a better sense of the relative efficacy of the different doses of the 5-α reductase inhibitors and minoxidil. The findings of this meta-analysis contribute to the comparative effectiveness literature for AGA therapies with regard to the compared interventions.

Figure 1.. Search Process

Schematic for identification of studies that were eligible for quantitative analyses.

Figure 2.. Risk of Bias Summary

Risk of bias across 6 domains for the 23 studies that were eligible for quantitative analyses is shown. Each domain received 1 of 3 judgments, namely, low risk of bias (denoted by green or the plus sign), unclear risk of bias (denoted by yellow or the question mark), and high risk of bias (denoted by red or the minus sign).

Figure 3.. Presentation of Treatments’ Surface Under the Cumulative Ranking Curve (SUCRA) via a Modified Kilim Plot

Names were prefixed with uppercase letters solely for the purpose of ordering. A treatment’s SUCRA corresponds to its overall rank for efficacy (higher values corresponding to greater efficacy). The vertical and horizontal axes correspond to the treatments and the end points, respectively. For example, SUCRA total at 24 weeks corresponds to change in total hair count (per square centimeters) after 24 weeks of therapy (ie, outcome 1). A color chart for SUCRA values is shown; red and green (which are arbitrarily chosen colors) correspond to lowest and highest SUCRA values, which, in turn, correspond to the least and the most effective treatment per this ranking metric, respectively.

Figure 4.. Kilim Plot for the Comparison of 15 Interventions and 4 End Points

Names were prefixed with uppercase letters solely for the purpose of ordering. Each cell represents the mean difference between the change in hair count after the respective duration in the treatment group and the change in hair count after the respective duration in the reference comparator. Our reference comparator (ie, control) was the arm for vehicle (placebo). Hence, the treatment effect for the control (ie, the reference) is 0; so, the nonzero values represented in the blue cells are pooled estimates from 1-group meta-analyses. P values close to green or red represent mean differences that are significantly more or less effective than the control, respectively; yellow corresponds to nonsignificant mean differences.