Finasteride (Proscar)

1. Health Canada Product Monograph — Finasteride

• Finasteride is indicated for the treatment and control of benign prostatic hyperplasia (BPH), an enlarged prostate gland.
• Finasteride is indicated to reduce the risk of acute urinary retention and the need for prostate surgery in men with BPH.
• Finasteride, in combination with the alpha-blocker doxazosin, is indicated to reduce the risk of BPH symptoms getting worse.
• Finasteride is not approved for the prevention of prostate cancer and is not indicated for use in women or children.

Contraindicated in pregnancy. Confirm pregnancy status and discuss alternative therapy with the prescriber before dispensing.

• Finasteride is contraindicated in women who are or may become pregnant.
• Finasteride can cause abnormal development of the external genitalia in a male fetus if a pregnant woman is exposed to the drug.
• Women who are or may be pregnant should avoid handling crushed or broken finasteride tablets, since the active drug could be absorbed through the skin.
• Intact, coated finasteride tablets prevent contact with the active ingredient during normal handling.

• Finasteride is not indicated for use in women, and it is not known whether finasteride passes into human breast milk.

• No dose adjustment is needed for older adults, although the elimination of finasteride is slower in men over 70 years of age.

• Finasteride is not indicated for use in children, and its safety and effectiveness in this age group have not been established.

• The recommended dose is one 5 mg tablet taken once daily, with or without food.
• No dose adjustment is needed for kidney impairment, even in patients with significantly reduced kidney function.
• No dose adjustment is needed for older adults, despite slower elimination of the drug in men over 70.
• If a dose is missed, an extra dose should not be taken; the next dose should be taken as usual at its regular time.
• A new baseline PSA level should be established about six months after starting finasteride, since the drug lowers PSA levels, and this baseline should be used to interpret future PSA test results.

If overdose is suspected, seek emergency medical attention immediately or contact your regional Poison Control Centre without delay.

• Patients have received single doses of finasteride up to 400 mg, and multiple daily doses of up to 80 mg per day for three months, without reported adverse effects.
• The product monograph does not describe a specific toxic syndrome associated with finasteride overdose, reflecting the drug's wide margin of safety at doses well above the recommended dose.

• Reduced sex drive (decreased libido) may occur.
• Erectile dysfunction (impotence) may occur.
• Decreased volume of ejaculate may occur.
• Abnormal or painful ejaculation may occur.
• Breast enlargement (gynecomastia) may occur.
• Breast tenderness may occur.
• Rash may occur.
• Weakness or fatigue (asthenia) may occur.
• Headache may occur.
• Dizziness may occur.
• Drowsiness (somnolence) may occur.
• A drop in blood pressure on standing (postural hypotension) may occur.
• Swelling in the hands or feet (peripheral edema) may occur.
• Shortness of breath (dyspnea) may occur.
• Runny nose (rhinitis) may occur.

Serious side effects require immediate discussion with the prescriber or emergency care.

• Finasteride may be associated with a higher risk of a more aggressive, high-grade form of prostate cancer, though it also lowers overall prostate cancer risk in some studies.
• Breast changes, including lumps, pain, nipple discharge, or enlargement, should be reported promptly, as rare cases of male breast cancer have been reported.
• Sexual side effects, including erectile dysfunction, decreased libido, and ejaculation disorders, have continued in some men even after stopping finasteride.
• Mood changes and depression, including rare reports of suicidal thoughts, have been reported in men taking finasteride.
• Serious allergic reactions, including swelling of the lips, tongue, throat, or face, hives, and itching, have been reported.
• Rare cases of muscle breakdown (rhabdomyolysis), muscle disease (myopathy), and muscle pain have been reported, sometimes reversible after stopping the drug.
• Male infertility and poor semen quality have been reported, which may improve after stopping finasteride.
• Testicular pain and blood in the semen have been reported.
• Seek urgent medical attention for a breast lump, nipple discharge, swelling of the face or throat, or thoughts of self-harm.

• Use with caution in patients with a large residual urine volume or severely reduced urinary flow, and monitor for obstruction of the urinary tract.
• Use with caution in patients being evaluated for prostate cancer, since finasteride lowers PSA levels and can mask or delay detection of cancer.
• Use with caution and monitor for mood changes or depression during treatment.
• Use with caution in patients taking medications with a narrow safety margin, such as phenytoin.
• A thorough urological evaluation should be done before starting finasteride to rule out prostate cancer or the need for immediate surgery.
• Use with caution in patients experiencing dizziness, drowsiness, or a drop in blood pressure on standing, particularly when finasteride is combined with the alpha-blocker doxazosin, which increases the rate of these effects.
• Use with caution and counsel patients to promptly report any breast changes, such as lumps, pain, or nipple discharge, given rare reports of male breast cancer.

• Contraindicated in women who are or may become pregnant.
• Contraindicated in patients with known hypersensitivity to finasteride or any ingredient in the product.

• No drug interactions of clinical importance have been identified with finasteride.
• Finasteride does not significantly affect the cytochrome P450 drug-metabolizing enzyme system.
• No clinically meaningful interactions were found in studies with propranolol, digoxin, glyburide, warfarin, theophylline, or antipyrine.
• Patients taking medications with a narrow safety margin, such as phenytoin, should be monitored carefully when starting finasteride, even though no specific interaction has been confirmed.
• Finasteride has been used without evidence of significant interactions alongside ACE inhibitors, acetaminophen, aspirin, alpha-blockers, beta-blockers, calcium channel blockers, cardiac nitrates, diuretics, H2 antagonists, statins, NSAIDs, quinolone antibiotics, and benzodiazepines.

• Finasteride can be taken with or without food; food does not affect how much of the drug is absorbed.

• Finasteride is taken once daily, at about the same time each day, and can be taken with or without food.

• Store at room temperature, between 15°C and 30°C, and protect from light to prevent discoloration.

• Finasteride works gradually; it may take several months to see improvement in urinary symptoms.
• Women who are or may become pregnant should not handle crushed or broken finasteride tablets.
• Report any breast lumps, pain, or nipple discharge to your pharmacist or doctor promptly.
• Tell your doctor you are taking finasteride before any PSA (prostate cancer screening) blood test, since it lowers PSA results.