Finasteride (topical)

Finasteride is a 5-alpha reductase inhibitor — it blocks conversion of testosterone to dihydrotestosterone (DHT), the androgen primarily responsible for hair-follicle miniaturization in androgenetic alopecia.¹ The oral form (1 mg daily) is FDA-approved for male pattern hair loss. Topical finasteride is a compounded formulation — typically a 0.25% solution or spray applied once daily to the scalp — that delivers the same DHT-blocking effect locally with substantially reduced systemic exposure.²

How topical compares to oral

Recent head-to-head and dose-finding trials show that topical 0.25% finasteride applied once daily produces hair-count improvements comparable to oral 1 mg daily, while systemic DHT suppression is significantly lower with the topical route.²³ For men who want the efficacy of finasteride but are concerned about the systemic side-effect profile — sexual side effects in particular — topical is a reasonable option.

Why systemic exposure matters

Oral finasteride suppresses serum DHT by roughly 70%. A small subset of users report persistent sexual side effects (post-finasteride syndrome), and the conversation about that risk is ongoing.⁴ Topical finasteride suppresses serum DHT by closer to 20–30% in published studies — most of the local effect with a fraction of the systemic load.² That difference doesn't eliminate risk, but it meaningfully reduces it.

What to expect

• Apply once daily to dry scalp; let it absorb before lying down or rinsing.
• Common protocol combines with topical minoxidil in a single compounded formulation.
• Transient shedding can occur in weeks 4–8 as miniaturized follicles cycle out.
• Visible regrowth or stabilization typically observed by 6–12 months. As with oral, ongoing use is required to maintain benefit.

Limitations

Topical finasteride is compounded, not FDA-approved, which means formulation quality depends on the compounding pharmacy. Standardized dosing and bioequivalence studies are still limited. Men with rapidly progressing hair loss may benefit more from the more reliably-absorbed oral form. Bloodwork at baseline and follow-up is less essential than with oral but still reasonable.