Does finasteride (a 5-alpha-reductase inhibitor) have a permanent effect on male fertility?

Finasteride's Effect on Male Fertility

Finasteride does not have a permanent effect on male fertility, as effects on fertility parameters are reversible within 6 weeks of discontinuation according to FDA labeling data. 1

Mechanism and Fertility Effects

Finasteride is a 5α-reductase inhibitor primarily used for male pattern hair loss and benign prostatic hyperplasia. Its effects on fertility parameters include:

• In animal studies, finasteride caused decreased fertility in rats when treatment continued for 24-30 weeks, but these effects were completely reversible within 6 weeks of discontinuation 1
• The FDA label specifically states that the decrease in fertility observed in finasteride-treated rats is secondary to effects on accessory sex organs (prostate and seminal vesicles) 1
• The drug can cause a modest decrease in ejaculate volume (approximately 11%) compared to placebo (8%), but this does not significantly impact overall fertility 2

Clinical Evidence on Reversibility

The evidence strongly supports that finasteride's effects on fertility are temporary:

• The FDA drug label indicates that fertility effects are reversible within 6 weeks of discontinuation 1
• A controlled study of young men (19-41 years) taking 1 mg finasteride daily for 48 weeks showed no significant effects on sperm concentration, total sperm per ejaculate, sperm motility, or morphology 2
• There have been documented cases of successful pregnancy after discontinuation of finasteride, even after long-term use (10 years), suggesting that the drug does not permanently impair fertility 3

Special Considerations for Subfertile Men

While finasteride's effects are generally reversible, there are important considerations for men with pre-existing fertility issues:

• In subfertile men, finasteride may have a more pronounced effect on semen parameters 4, 5
• A study of men presenting to a fertility clinic showed an average 11.6-fold increase in sperm counts after finasteride discontinuation 5
• Among men with severe oligospermia (<5 million/mL), 57% had counts increase to >15 million/mL after stopping finasteride 5

Clinical Recommendations

1. For men planning pregnancy:

   • Consider discontinuing finasteride if actively trying to conceive
   • Allow at least 6 weeks after discontinuation before attempting conception
   • Monitor semen parameters if conception is delayed

2. For men with known fertility issues:

   • Use finasteride with caution as it may amplify existing fertility problems 4, 5
   • Consider baseline semen analysis before starting treatment
   • Discontinue finasteride in subfertile men with oligospermia 5

Important Caveats

• While sexual side effects (erectile dysfunction, decreased libido) may persist after discontinuation in some men 6, the evidence does not suggest permanent effects on fertility parameters
• The American Urological Association acknowledges post-finasteride syndrome but focuses primarily on sexual function rather than fertility effects 7
• Men should be counseled about potential temporary effects on fertility before starting treatment 7

Monitoring Recommendations

• For men concerned about fertility, consider periodic semen analysis during treatment
• If abnormalities are detected, discontinuation of finasteride should be considered
• Allow adequate time (at least 6 weeks) after discontinuation for reversal of any effects before reassessment

The evidence consistently shows that while finasteride may temporarily affect fertility parameters in some men, these effects are reversible upon discontinuation of the medication, with no evidence supporting permanent impairment of male fertility.