Finasteride is a widely used medication that belongs to the drug class known as 5-alpha reductase inhibitors. It was developed to address conditions driven by excess dihydrotestosterone (DHT), a potent metabolite of testosterone. By selectively inhibiting the type II 5-alpha reductase enzyme, finasteride lowers circulating and tissue DHT levels, often by 60–90% depending on dose and tissue studied. This reduction has two primary clinical effects: shrinking the prostate gland in men with benign prostatic hyperplasia (BPH), and slowing or reversing miniaturisation of hair follicles in men with androgenetic alopecia (male pattern baldness).
Introduced in the 1990s, finasteride is now available worldwide in multiple branded and generic forms. Its clinical impact extends beyond symptom relief; in BPH it reduces the long-term risk of acute urinary retention and surgery. In dermatology, it remains one of the few proven pharmacological options for male hair loss. It is taken orally, is well absorbed, and achieves stable blood levels quickly. Its effects are reversible: when discontinued, DHT levels return to baseline within about two weeks, and any clinical benefit (hair retention or prostate size reduction) diminishes over months. This means finasteride is generally prescribed as a long-term therapy if tolerated.
Because finasteride interferes with a fundamental androgen pathway, its use has been studied carefully for safety, sexual function, psychological effects, and cancer risk. While effective and usually well tolerated, it is not without controversy, particularly surrounding reports of persistent side effects. Clinicians and patients weigh these concerns against its clear and evidence-based benefits in prostate health and hair preservation.
Finasteride has two licensed primary uses:
Additional uses (off-label) include management of hirsutism in women, adjunctive therapy in transgender women as part of gender-affirming care, and experimental use in some prostate cancer contexts. These uses are less common and typically require specialist oversight.
Patients should be counselled that improvement may take months and adherence is key. For BPH, symptomatic relief can take 6 months or more, while for alopecia, visible benefit typically appears after at least 3 months of consistent therapy.
Like all medicines, finasteride can cause side effects, though not everyone experiences them. Most side effects relate to its impact on androgen pathways.
Most men tolerate finasteride well. If side effects become troublesome, options include stopping the drug, lowering dose, or switching to alternatives. Always consult a clinician before making changes.
Patients should receive baseline evaluations including PSA and prostate exam (for BPH) and should be followed regularly during therapy.
Finasteride is metabolised by the CYP3A4 pathway, but it has minimal clinically important drug interactions. Still, caution is sensible when combining with:
Because interaction potential is low, finasteride is generally considered safe even in patients taking multiple other medications. Patients should, however, always share a full medication list with their doctor.
Overdose: Finasteride is well tolerated even at doses many times the therapeutic level. No specific antidote exists. Treatment is supportive—monitor for adverse symptoms and provide reassurance.
Accidental exposure: Women who are pregnant should not handle crushed tablets. If accidental contact occurs, the area should be washed with soap and water and medical advice sought.
Missed dose: Take as soon as remembered unless close to the next scheduled dose. If nearly time for the next dose, skip the missed tablet. Do not double up. Consistency over weeks and months is more important than occasional missed doses.
Finasteride tablets are film-coated and stable under normal conditions. Proper storage ensures effectiveness for the full shelf life.
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