How finasteride works
Finasteride is a selective inhibitor of type II 5-alpha reductase. It reduces DHT levels, which can slow follicle miniaturization. In studies of androgenetic alopecia, many people maintain hair and some see modest improvement with consistent use.
Clinical trial results
In pivotal trials, participants taking finasteride were more likely to maintain or increase hair count compared with placebo. Visible changes typically begin over months, with the best chance of benefit when treatment is used consistently and long-term.
Limitations
Finasteride is less effective for extensive Norwood V–VII loss and does not address hair loss caused by conditions other than androgenetic alopecia. Results are dependent on continued use — discontinuation leads to gradual return of hair loss within 6–12 months.
Safety profile
The most commonly reported side effects are sexual in nature (for example, decreased libido or erectile changes). These effects were uncommon in trials but can occur. Discuss risks, benefits, and alternatives with your prescribing clinician.