Finasteride is a synthetic hormone-modulating agent primarily used in men’s health. It belongs to the class of 5-alpha-reductase inhibitors, which block the conversion of testosterone to dihydrotestosterone (DHT). In Hong Kong, finasteride is a prescription-only medication (Rx) supplied as a 5 mg oral pill. It is available as a generic product and marketed under brand names such as Proscar and Propecia in various regions.
Finasteride selectively inhibits the type II isozyme of the enzyme 5-alpha-reductase. By reducing the enzymatic conversion of testosterone to DHT, the drug lowers circulating and tissue DHT levels. DHT is a potent androgen that drives prostate enlargement and contributes to hair-follicle miniaturisation. Lowering DHT therefore:
Finasteride is well-absorbed after oral administration, achieving peak plasma concentrations within 1-2 hours. It is extensively metabolised in the liver (primarily by CYP3A4) and excreted mainly in the feces. The biological half-life ranges from 5 to 7 days, allowing steady-state concentrations to be reached after about a month of daily dosing.
Finasteride is FDA- and EMA-approved for the following indications:
In Hong Kong, the primary approved use of the 5 mg formulation aligns with the BPH indication. Treatment is generally considered for men experiencing moderate to severe lower urinary tract symptoms attributable to prostate enlargement.
Finasteride has been explored for several off-label uses, though these are not approved by regulatory agencies in Hong Kong. Research contexts include:
Off-label use requires medical supervision and individualized risk assessment.
These effects are reported in more than 1 % of users and are typically transient. If persistent, patients should discuss management options with their prescriber.
Standard dosing: One 5 mg tablet taken orally once daily, preferably at the same time each day.
Special populations:
Hepatic impairment: Initiate at 2.5 mg daily; adjust based on clinical response and liver function tests.
Elderly: No routine dose reduction required, but monitor for side effects.
Administration: Swallow the pill whole with a glass of water. Do not crush or chew.
Missed dose: Take the missed tablet as soon as remembered unless it is near the time of the next dose; do not double-dose.
Overdose: Symptoms may include dizziness, fainting, or severe hypotension. Seek emergency medical care; supportive care is the primary treatment.
Discontinuation: Finasteride can be stopped abruptly, but patients should be aware that BPH symptoms may return gradually. No tapering is required.
This article provides educational information about finasteride and is not a substitute for professional medical advice. Treatment decisions, including use for unapproved indications, must be made under the guidance of a qualified healthcare provider. The content is intended for informational purposes and does not constitute medical recommendations. Always consult a physician before starting, stopping, or changing any medication regimen.
Finasteride is metabolised in the liver, so mild hepatic impairment may warrant a lower starting dose (e.g., 2.5 mg daily). Your prescriber will assess liver function tests and adjust the regimen accordingly.
Yes. Finasteride typically reduces PSA concentrations by roughly 50 %. Clinicians should double the measured PSA value to approximate the true level when monitoring for prostate disease.
Finasteride does not directly influence blood clotting pathways, but routine monitoring is advisable when combined with anticoagulants such as warfarin or direct oral anticoagulants.
There are no known pharmacodynamic interactions between finasteride and common antihypertensives. However, always inform your doctor of all concurrent medicines.
Take the missed tablet as soon as you remember, unless it is nearly time for your next dose. Then, skip the missed dose and continue with your regular schedule; do not double-dose.
Weight change is not a recognized side effect of finasteride. If you notice unexplained weight fluctuations, discuss them with your healthcare provider.
Finasteride can be taken with or without food, and no specific diet is required. Maintaining a balanced diet supports overall prostate health.
The 1 mg dose of finasteride (often marketed as Propecia) is approved for male-pattern hair loss. The 5 mg formulation discussed here is primarily indicated for BPH.
Most men notice a gradual improvement within 3 to 6 months of consistent daily dosing, although full benefit may take up to a year.
Finasteride is not classified as a controlled substance and is not typically targeted in standard employment drug screens. However, specific sports or occupational testing programs may list it for disclosure.
