Finasteride Drug Profile

What is Finasteride?

Finasteride is a synthetic 5-alpha-reductase inhibitor primarily used to treat benign prostatic hyperplasia (enlarged prostate) and male pattern baldness. It belongs to a class of medications that block the conversion of testosterone to dihydrotestosterone (DHT), a hormone that contributes to prostate enlargement and hair loss. Finasteride is available only by prescription and is taken orally as a tablet.

Uses

Finasteride has several FDA-approved and documented uses:

• Benign Prostatic Hyperplasia (BPH): Reduces prostate size and improves urinary flow in men with enlarged prostate glands
• Male Pattern Baldness: Slows hair loss and promotes hair regrowth in men with androgenetic alopecia
• Combination Therapy for BPH: Often used alongside alpha-blockers like doxazosin for enhanced treatment of urinary symptoms
• Prostate Cancer Prevention: May reduce the risk of developing prostate cancer, though this remains a subject of ongoing research

How it works

Finasteride works by blocking the enzyme 5-alpha-reductase, which converts testosterone into dihydrotestosterone (DHT). By reducing DHT levels by approximately 70%, finasteride helps shrink enlarged prostate tissue and slows the miniaturization of hair follicles that leads to male pattern baldness. This mechanism addresses the root hormonal cause of both conditions rather than just treating symptoms.

Side effects

Common side effects include:

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• Decreased libido
• Erectile dysfunction
• Reduced ejaculate volume
• Breast tenderness or enlargement
• Dizziness
• Weakness
• Headache
• Skin rash

Serious side effects to watch for:

• Severe depression or mood changes
• Persistent sexual dysfunction after discontinuation
• Breast lumps or discharge
• Severe allergic reactions with swelling of face, lips, or throat
• Testicular pain or swelling

Warnings and precautions

• Pregnancy Category X: Finasteride is contraindicated in women who are or may become pregnant, as it can cause birth defects in male fetuses. Pregnant women should not handle crushed or broken tablets.
• PSA Testing: Finasteride can lower prostate-specific antigen (PSA) levels by approximately 50%, which may affect prostate cancer screening. Healthcare providers should adjust PSA interpretations accordingly.
• Blood Donation: Men taking finasteride should not donate blood during treatment and for at least one month after stopping, to prevent exposure to pregnant women.
• Liver Function: Use with caution in patients with liver disease, as the drug is metabolized hepatically.
• Age Considerations: Not recommended for use in children, and elderly patients may be more sensitive to side effects.

Interactions

• Saw Palmetto: May have additive effects in reducing DHT levels, potentially increasing side effects
• Testosterone Supplements: May counteract finasteride’s effects by increasing substrate for DHT conversion
• Alpha-blockers (doxazosin, tamsulosin): Often used together for BPH but may increase risk of dizziness and low blood pressure
• Warfarin: Limited data suggests potential for altered anticoagulation effects, requiring monitoring
• St. John’s Wort: May decrease finasteride effectiveness by increasing liver metabolism
• Ketoconazole: May increase finasteride blood levels by inhibiting liver enzymes
• Rifampin: May decrease finasteride effectiveness by increasing drug metabolism
• Dutasteride: Should not be used together as both are 5-alpha-reductase inhibitors with overlapping effects

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Dosage

For benign prostatic hyperplasia: The typical dose is 5 mg once daily, taken with or without food. For male pattern baldness: The standard dose is 1 mg once daily. Treatment effects for hair loss may take 3-6 months to become noticeable, while prostate symptoms may improve within 6-12 months. Dosage should always be determined by a healthcare provider based on individual patient factors, medical history, and treatment goals. Patients should continue taking finasteride as prescribed, as discontinuing the medication will reverse its benefits over time.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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