Finasteride [For Androgenic Alopecia]

Approved Indication:

• Androgenic Alopecia (Male Pattern Hair Loss):
  Finasteride 1 mg is indicated for the treatment of male pattern hair loss (androgenic alopecia) in men aged 18 to 41 years to increase hair growth and prevent further hair loss at the vertex (crown) and anterior mid-scalp area.

Important Off-Label / Clinically Accepted Uses:

• Androgenic Alopecia in Postmenopausal Women (off-label, selective use):
  Use in women remains controversial and is not approved, but low-dose finasteride has been used off-label in select postmenopausal women with androgenic alopecia under specialist supervision.
• Female Hirsutism (off-label):
  Occasionally used as an antiandrogen to reduce excess hair growth in women, though not FDA approved for this use.
• Adjunct to Hair Transplantation:
  Used to prevent miniaturization of native hair and improve long-term graft survival.

Route of Administration: Oral

Adults (Males):

• Dose: 1 mg orally once daily
• Timing: Can be taken with or without food
• Duration: Minimum of 3 to 6 months of daily use is required to assess efficacy. Continued use is necessary to maintain benefits. Discontinuation results in reversal of effects within 12 months.

Pediatrics:

• Not indicated or approved for use in children or adolescents.

Females:

• Not approved for androgenic alopecia. Contraindicated in women of childbearing potential due to risk of fetal harm.

Elderly:

• Not indicated for age-related hair loss. No dosage adjustment specified, but the safety and efficacy in men over 41 have not been well established for this indication.

Renal/Hepatic Impairment:

• No specific dose adjustment required, but caution is advised in hepatic impairment due to primary hepatic metabolism.

Finasteride is a competitive and selective inhibitor of type II 5α-reductase, an intracellular enzyme that converts testosterone to dihydrotestosterone (DHT), a potent androgen. In androgenic alopecia, elevated scalp DHT levels shrink hair follicles, shorten the anagen (growth) phase, and cause follicular miniaturization. By reducing scalp and serum DHT concentrations by up to 60%, finasteride reverses the miniaturization process, prolongs the growth phase, and stimulates regrowth in hair follicles responsive to androgen blockade, particularly in the vertex and mid-scalp area.

• Absorption: Oral bioavailability ~65%, unaffected by food
• Peak Plasma Time: ~1–2 hours after dosing
• Distribution: Widely distributed; ~90% plasma protein binding
• Metabolism: Extensively metabolized in the liver via CYP3A4
• Active Metabolites: Two minor, weakly active metabolites
• Elimination Half-life: ~5–6 hours (young men); up to 8 hours in elderly
• Excretion: 39% via urine (metabolites), 57% via feces
• Steady-State Concentration: Achieved within 3 days of daily dosing

• Pregnancy:
  Contraindicated. Finasteride is teratogenic and may cause abnormalities in external genitalia of a male fetus. Women who are or may become pregnant must not handle crushed or broken tablets.
• Lactation:
  Not indicated in women. Unknown whether finasteride is excreted in breast milk.
• Recommendation:
  Contraindicated in women of childbearing potential. Tablets should be handled with care, especially by pregnant women.

• Primary Class: 5-Alpha Reductase Inhibitor
• Subclass: Type II 5α-reductase selective inhibitor
• Pharmacological Category: Antiandrogen (for dermatologic use in androgenic alopecia)

• Known hypersensitivity to finasteride or any component of the formulation
• Women who are or may become pregnant (teratogenic risk)
• Pediatric patients
• Use in women with active liver disease (precautionary contraindication)

• Pregnancy Risk:
  Finasteride is highly teratogenic to male fetuses. Avoid any exposure during pregnancy.
• Breast Cancer Risk (Males):
  Rare reports of male breast cancer; monitor for nipple discharge, lumps, or breast tenderness.
• Depression and Suicidal Ideation:
  Cases of depression, mood changes, and suicidal thoughts have been reported. Monitor for psychiatric symptoms.
• Post-Finasteride Syndrome (PFS):
  A controversial condition involving persistent sexual, neurological, and psychological side effects after discontinuation. Not fully understood, but patients should be informed.
• Hepatic Impairment:
  Metabolized in the liver; use cautiously in hepatic dysfunction.
• Prostate Cancer Risk (at 5 mg doses):
  At higher doses used for BPH, finasteride may lower PSA levels and potentially delay prostate cancer diagnosis. Not relevant at 1 mg for alopecia but should be noted.

Common (≥1%):

• Reproductive System:
• Decreased libido
• Erectile dysfunction
• Decreased ejaculate volume
• Testicular pain
• Neurologic:
• Depression
• Anxiety (less frequent)
• Dermatologic:
• Rash (infrequent)

Uncommon (<1%):

• Breast tenderness or enlargement (gynecomastia)
• Ejaculation disorders
• Infertility (reversible in some cases)

Rare/Serious:

• Male breast cancer
• Persistent sexual dysfunction after discontinuation (PFS)
• Hypersensitivity reactions (including swelling of the lips and face)

Timing:
Sexual side effects typically occur within the first months of therapy and may resolve with continued use or upon discontinuation. Psychiatric symptoms may appear at any point.

• CYP3A4 Substrates/Inhibitors:
  Finasteride is metabolized by CYP3A4, but clinically significant interactions are unlikely at the 1 mg dose.
• No Major Drug-Food or Drug-Alcohol Interactions:
  Alcohol does not interfere with efficacy, but both may independently affect libido.
• Other Antiandrogens or Hormonal Agents:
  Concurrent use may enhance antiandrogenic effects and increase side effect risk.
• Laboratory Test Interference:
  Finasteride reduces serum PSA levels by ~50%, which may mask early detection of prostate cancer (relevant at higher doses).

• Regulatory Warning (2022–2024):
  Health authorities in some countries (e.g., Canada, France, South Korea) have issued updated warnings about depression, anxiety, and suicidal ideation with finasteride, even at 1 mg doses.
• MHRA and FDA Updates:
  Advised clearer patient counseling regarding risks of mood disorders and persistent sexual side effects.
• Guideline Reinforcement:
  Finasteride 1 mg remains a first-line pharmacologic therapy for male pattern hair loss in international dermatology and trichology guidelines.
• Biosimilars & Combination Use:
  Combination with topical minoxidil is widely accepted for improved efficacy and long-term outcomes.

• Temperature: Store at 20°C to 25°C (controlled room temperature)
• Permitted Range: Excursions between 15°C and 30°C are acceptable
• Light Protection: Store in original packaging to protect from moisture and light
• Handling: Tablets should not be crushed or broken, especially by women who are or may become pregnant
• Shelf Life: As per manufacturer’s labeling (typically 2–3 years)