Is finasteride (a 5-alpha-reductase inhibitor) safe for use in women?

Finasteride Use in Women

Finasteride is absolutely contraindicated in women who are or may become pregnant due to severe teratogenic risk to male fetuses, but can be considered for postmenopausal women or women using reliable contraception for specific dermatologic conditions, particularly hirsutism and female pattern hair loss. 1

Absolute Contraindications

Pregnancy represents an absolute contraindication to finasteride use in women. The FDA explicitly states that finasteride is contraindicated when women are or may potentially be pregnant because it causes abnormalities of external genitalia in male fetuses 1. Animal studies demonstrate:

• Dose-dependent hypospadias occurring in 3.6-100% of male offspring at doses 0.1 to 86 times the human dose 1
• Decreased prostatic and seminal vesicular weights in male offspring 1
• Decreased anogenital distance at doses as low as 0.003 times the maximum recommended human dose 1

Women of childbearing potential must not handle crushed or broken finasteride tablets due to potential transdermal absorption that could harm a male fetus 1.

When Finasteride Can Be Used in Women

Postmenopausal Women

For postmenopausal women with female pattern hair loss, oral finasteride 5 mg daily is effective and safe, particularly when combined with topical minoxidil or estradiol. 2 A systematic review of 2,683 patients across 65 studies found that finasteride can be used in women aged 6-88 years, with most studies using 6-12 month treatment durations 3.

Premenopausal Women with Reliable Contraception

Premenopausal women may use finasteride only if they maintain highly reliable contraception throughout treatment. 3, 2 The evidence supports:

• Hirsutism/PCOS: Randomized controlled trials specifically recommend finasteride for women with hirsutism or polycystic ovarian syndrome 3
• Female pattern hair loss: Prospective and retrospective studies show improvement in normoandrogenic women with FPHL 3, 2
• Frontal fibrosing alopecia: Observational studies suggest potential benefit 3

Dosing Recommendations

The effective dose for women is 5 mg daily (higher than the 1 mg dose used for male pattern hair loss). 2 Treatment protocols from the systematic review show:

• Oral finasteride doses ranging from 0.5-5 mg/day 3
• Treatment duration of 6-12 months in 57.6% of studies 3
• Monotherapy used in 88.9% of cases 3
• Continuous use recommended in 96.4% of protocols 3

Ten out of 14 studies meeting inclusion criteria reported high rates of alopecia recovery in women taking finasteride. 2

Topical Finasteride Alternative

Topical finasteride formulations may offer a safer alternative by minimizing systemic absorption and teratogenic risk. 2 Evidence suggests topical finasteride is more effective than other topical formulas for treating hair loss in women 2, though this remains an area requiring further investigation 3, 4.

Safety Profile in Women

Sexual side effects documented in men (erectile dysfunction, decreased libido, ejaculatory dysfunction) are not applicable to women. 5, 6 The primary safety concern remains teratogenicity, not the sexual dysfunction profile seen in male patients 1.

Finasteride does not affect testosterone or estradiol levels, and luteinizing hormone levels remain unchanged during chronic treatment. 7 This hormonal profile suggests that libido and sexual function should theoretically be preserved in women, though female-specific sexual function data is limited 7.

Critical Clinical Pitfalls

1. Never prescribe to women without documented reliable contraception or confirmed postmenopausal status 1
2. Counsel patients that male partners taking finasteride pose negligible risk - semen concentrations are 50-100 fold less than the dose that affects DHT levels 1
3. Recognize that most evidence comes from off-label use - finasteride is not FDA-approved for any indication in women 3, 2
4. Long-term safety data in women remains limited - most studies evaluate 6-12 month treatment periods 3