finasteride at a glance
Medicine class
5-alpha-reductase inhibitor
Main uses
Male pattern hair loss in men; benign prostatic hyperplasia with an enlarged prostate.
Important test
Finasteride lowers PSA. Tell the clinician interpreting any PSA result that you take it.
What is finasteride used for?
Selected UK products are licensed for:
Male pattern hair loss in men, to increase hair growth and help prevent further loss.
Benign prostatic hyperplasia with an enlarged prostate, including improving urinary symptoms and reducing the risk of acute urinary retention or surgery.
How does finasteride work?
Finasteride blocks type II 5-alpha-reductase, reducing conversion of testosterone to dihydrotestosterone (DHT). Lower DHT can reduce prostate enlargement and limit DHT-related miniaturisation of scalp hair follicles.
finasteride preparations and strengths
Tablet
Route: Oral
Strengths: 1 mg, 5 mg
How to take finasteride
Follow the label and prescriber's instructions.
Swallow the film-coated tablet whole with water.
It may be taken with or without food.
Do not crush or break tablets. This also prevents pregnant people from contacting the active ingredient.
finasteride side effects
Common or expected effects
- Reduced interest in sex
- Difficulty getting or maintaining an erection
- Ejaculation problems, including reduced semen volume
Get urgent medical advice
- Depression, suicidal thoughts or marked mood changes
- Swelling of the face, lips, tongue or throat, or difficulty breathing
- A breast lump, breast pain or swelling, or nipple discharge
finasteride in pregnancy
Finasteride is contraindicated during pregnancy because exposure could affect development of a male fetus. Anyone pregnant or potentially pregnant should not handle crushed or broken tablets; intact film-coated tablets prevent contact during normal handling. Exposure through semen is very small and considered unlikely to cause harm, but discuss concerns with a healthcare professional.
finasteride while breastfeeding
Finasteride is not normally used by women, and it is unknown whether it passes into human milk. Seek specialist or prescriber advice if its use is being considered while breastfeeding.
finasteride interactions
Clinically important medicine interactions are uncommon, but these points matter:
Other finasteride products or dutasteride
Do not duplicate 5-alpha-reductase inhibitor treatment unless specifically directed by a specialist.
Strong CYP3A4 inhibitors or inducers
They may alter finasteride concentrations, although product information considers a clinically important effect unlikely within established safety margins.
Common questions about finasteride
Answers are fully visible for fast scanning and source review.
What is finasteride used for in the UK?
Depending on the product, it is licensed for male pattern hair loss in men or benign prostatic hyperplasia with an enlarged prostate.
Does finasteride affect a PSA blood test?
Yes. It lowers PSA, so the clinician requesting or interpreting the test must know that you take finasteride.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.