Oral minoxidil (low-dose, for hair) — evidence review

Regulatory status: prescription medication (direct arteriolar vasodilator / potassium-channel opener), used off-label for hair loss

Mechanism evidence: human

• **Lowering of severe, refractory blood pressure** (approved use; not a hair claim).
• **Increased scalp hair density / hair count in male androgenetic alopecia (AGA).**
• **Increased scalp hair density / hair count in female-pattern hair loss (FPHL).**
• **Increased hair-shaft diameter / thickness in AGA / FPHL.**
• **Reduced shedding** (Sinclair shedding score or similar).
• **Global photographic improvement** of the vertex and frontal scalp.
• **Superiority of oral over topical 5% minoxidil** for density (a common claim; tested and not supported as superiority).
• **Alopecia areata** — cosmetic regrowth.
• **Chronic telogen effluvium** — less shedding.
• **Lichen planopilaris / other scarring alopecias** — thicker background hair (not disease modification of the scar).

Low-dose oral minoxidil increases scalp hair density in androgenetic alopecia in both sexes. The best human evidence is small 24-week RCTs against **topical** minoxidil, plus one 5 mg open-label male count study (+35 total hairs/cm²). Oral is **not superior** to topical 5% on hair count (Penha 2024; Ramos 2020; 4-RCT SMD 0.02). Women in trials sit at **0.25–1 mg**; men who gained density sat at **2.5–5 mg**; **0.25 mg was a null in men**. Hypertrichosis is the dominant adverse effect and is dose- and sex-dependent (15% in the 1,404-patient series; 49–93% at 5 mg in men; ~80% on old antihypertensive doses). Fluid retention and tachycardia are uncommon at LDOM amounts (about 1% each in Vañó-Galván) and common at 10–40 mg. **Pericardial effusion is in the boxed warning, occurred in ~3% of labeled hypertensives, and has FAERS plus case-report signals at hair-range amounts — rare, not imaginary, worse with cardiac impairment, and sometimes a compounding error.** Oral minoxidil remains an **antihypertensive**. Hair use is **off-label**. Topical 5% is a different, licensed intervention with a local-irritation safety map and almost no systemic hemodynamic signal.