BMA Concise Guide to Medicine & Drugs


Brand names Propecia, Proscar

Used in the following combined preparations None


Drug group Drug for urinary disorders

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic Yes


Finasteride is an anti-androgen drug (see Male sex hormones) used to treat benign prostatic hyperplasia (BPH), in which the prostate gland, which surrounds the urethra, increases in size, making urination difficult. The drug works by gradually shrinking the prostate gland, which improves urine flow and other obstructive symptoms such as difficulty in starting urination.

Because finasteride is excreted in semen and can feminize a male fetus, you should use a condom if your sexual partner may be, or is likely to become, pregnant. Also, women of childbearing age should not handle broken or crushed tablets because small quantities of the drug are absorbed through the skin.

The symptoms of BPH are similar to those of prostate cancer and so the drug is used only when the possibility of cancer has been ruled out.

Finasteride is also used, at a lower dose, to reverse male-pattern baldness by preventing the hair follicles from becoming inactive. Noticeable improvements may take about three months but will disappear within a year of treatment being stopped.


Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets.

Frequency and timing of doses Once daily.

Adult dosage range Prostate disease 5mg. Male-pattern baldness 1mg.

Onset of effect Within 1 hour, but beneficial effects may take several months.

Duration of action 24 hours.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children. Protect from light.

Missed dose Do not take the missed dose, but take your next scheduled dose as usual.

Stopping the drug Do not stop taking the drug without consulting your doctor; stopping the drug may lead to worsening of the underlying condition.

Exceeding the dose An occasional unintentional extra dose is unlikely to cause problems. But if you notice any unusual symptoms, or if a large overdose has been taken, notify your doctor.


Most people experience very few adverse effects when taking finasteride; erectile dysfunction (impotence), decreased libido, reduced ejaculate volume, and breast swelling or tenderness are the most common. More rarely, testicular pain may occur. If a rash, swelling of the lips, or wheezing develop, you should stop taking the drug and seek urgent medical attention.


No drug interactions but finasteride does interfere with the prostate specific antigen (PSA) screening test for prostate cancer.


Be sure to tell your doctor if:

· You have liver problems.

· You are taking other medicines.

Pregnancy Not prescribed.

Breast-feeding Not applicable.

Infants and children Not prescribed.

Over 60 No special problems.

Driving and hazardous work No special problems.

Alcohol No special problems.


Treatment with finasteride for benign prostatic hyperplasia and male-pattern baldness is reviewed after about six months to see if it has been effective. Long-term use of the drug carries a small increase in the risk of men developing breast cancer.