There Is a Positive Dose-Dependent Association between Low-Dose Oral Minoxidil and Its Efficacy for Androgenetic Alopecia: Findings from a Systematic Review with Meta-Regression Analyses

BACKGROUND: Recently, low-dose oral minoxidil (LDOM) has entered the landscape of therapies for androgenetic alopecia (AGA). We determined whether using LDOM is associated with improving AGA in a dose-dependent manner; secondarily, we examined whether a dose-dependent association also exists for safety. METHODS: Systematic searches were conducted in PubMed and Scopus to identify studies that would be eligible for our quantitative analyses; the logistics of our analyses was determined by the data we gathered. RESULTS: Six studies were eligible for quantitative analyses; we conducted meta-regressions. We found that, for persons with AGA, increasing the dosage of LDOM by 1 mg/day was − after six months − significantly associated with an expected sex-adjusted increase in hair diameter (mean difference = 1.4 μm, p = 0.01), total hair density (mean difference = 47.1 hairs/cm², p = 0.007), terminal hair density (mean difference = 9.1 hairs/cm², p = 0.001), risk of hypertrichosis (mean difference = 17.9%, p = 0.006), and cardiovascular adverse events (mean difference = 4.8%, p = 0.004). CONCLUSIONS: Our study produced new evidence as our work is the first to show a positive dose-dependent association between the use of LDOM and change in hair diameter, hair density, risk of hypertrichosis, and cardiovascular adverse events for persons with AGA. Future randomized trials could produce causal evidence that would corroborate these dose-dependent associations.