Finasteride

Finasteride is a 5-alpha reductase inhibitor available in two strengths: 1 mg for male-pattern hair loss (androgenetic alopecia) and 5 mg for benign prostatic hyperplasia (BPH).

The active substance is the same in both cases; only the indication and dose differ.

Finasteride blocks the type II isoenzyme of 5-alpha reductase, which converts testosterone to its more potent metabolite dihydrotestosterone (DHT).

In the scalp, DHT drives the miniaturisation of genetically susceptible hair follicles. In the prostate, DHT stimulates glandular growth.

By lowering DHT levels, finasteride slows hair loss and reduces prostate volume.

Hair Loss (1 mg)

At the 1 mg dose, finasteride lowers scalp DHT by approximately 60-70%. Clinical trials show that around 83% of men maintain or increase hair count over two years.

The benefit is seen predominantly at the vertex and mid-scalp.

Benign Prostatic Hyperplasia (5 mg)

At the 5 mg dose, finasteride reduces prostate volume by 20-30% over 6-12 months, improves urinary flow, and significantly reduces the risk of acute urinary retention and surgical intervention.

It approximately halves the serum PSA level, which must be accounted for in prostate cancer screening.

How to Take Finasteride

Swallow one tablet daily with water, with or without food. Take it at the same time each day for consistent blood levels.

For Hair Loss (1 mg)

Expect at least three to six months of daily use before visible improvement. Hair loss resumes within 6-12 months of stopping. Long-term use is needed to maintain results.

For BPH (5 mg)

At least six months of continuous treatment is needed before the full benefit on urinary symptoms and prostate volume is seen.

Handling Precautions

Women who are or may become pregnant must not handle broken or crushed finasteride tablets.

The drug can be absorbed through the skin and may cause abnormalities of the external genitalia in a developing male foetus. Intact coated tablets are safe to handle.

Androgenetic Alopecia

• 1 mg once daily (men aged 18-41)

Benign Prostatic Hyperplasia

• 5 mg once daily

Duration

• Hair loss: long-term, reviewed periodically
• BPH: long-term; prostate regrows on stopping

Renal Impairment

• No dose adjustment

Hepatic Impairment

• Limited data; use with caution

Not For Use In

• Women
• Children and adolescents
• Patients using both 1 mg and 5 mg concurrently

Common (up to 1 in 10 patients, especially in the first year)

• Decreased libido
• Erectile dysfunction
• Reduced ejaculate volume

Uncommon (up to 1 in 100 patients)

• Breast tenderness or gynaecomastia
• Ejaculation disorder
• Rash

Rare (up to 1 in 1,000 patients)

• Depression
• Allergic reactions (pruritus, urticaria, angioedema)
• Testicular pain
• Elevated liver enzymes

Post-Marketing Reports (frequency indeterminate)

• Persistent sexual dysfunction reported after discontinuation (causality debated)
• Anxiety
• Male breast cancer (very rare; causal link not established)

Sexual side effects are the most commonly cited reason for discontinuation.

They occur in a minority and usually resolve on stopping, though persistent effects have been reported in a small number of cases.

PSA and Prostate Cancer Screening

Finasteride 5 mg approximately halves serum PSA. Any sustained rise in PSA during treatment, even within the normal range, should be investigated.

Finasteride 1 mg also reduces PSA, though to a lesser degree. Inform any new doctor or laboratory that you take finasteride.

Sexual Side Effects

Discuss the possibility of decreased libido, erectile dysfunction, and persistent post-discontinuation effects with the patient before starting treatment.

Female Exposure

Pregnant women and women who may become pregnant must not handle crushed or broken tablets. Finasteride is classified as a teratogen for male foetuses. Intact tablets have a protective coating.

Mood

Monitor for depression or low mood. Report persistent changes to your prescriber.

Blood Donation

Do not donate blood while taking finasteride or for one month after stopping, to prevent the possibility of a pregnant woman receiving the drug via transfusion.

Do not take finasteride if you:

• Are a woman (not indicated; teratogenic risk in pregnancy)
• Are a child or adolescent
• Have a known hypersensitivity to finasteride or any excipient
• Are taking both the 1 mg and 5 mg dose simultaneously

Women of childbearing potential must avoid contact with crushed or broken tablets.

Finasteride is not licensed for use in women for hair loss, and its use in premenopausal women of childbearing potential is contraindicated without highly effective contraception.