The prescribing information for Propecia (finasteride 1 mg) lists male infertility and/or poor seminal quality among adverse reactions identified during post-approval use. It says normalization or improvement of seminal quality has been reported after discontinuation of finasteride. A randomized trial of 1 mg finasteride in young men reported no significant effects on sperm concentration, total sperm per ejaculate, sperm motility or morphology. Other studies used a different dose or a different group of men, so each study below is labeled with its dose.
What the label says
The Propecia Patient Information lists, among effects reported in general use, male infertility and/or poor quality of semen.
On ejaculate volume, the label states that in a study of finasteride 1 mg daily in healthy men, a median decrease in ejaculate volume of 0.3 mL (-11%) compared with 0.2 mL (-8%) for placebo was observed after 48 weeks of treatment.
The label also lists, among adverse reactions identified during post-approval use, sexual dysfunction that continued after discontinuation of treatment, including erectile dysfunction, libido disorders, ejaculation disorders, and orgasm disorders.
Studies of finasteride 1 mg
A 1999 trial in the Journal of Urology was double-blind, placebo controlled and multicenter. It randomized 181 men 19 to 41 years old to 1 mg finasteride or placebo for 48 weeks, followed by a 60-week off-drug period. Of the 181 men, 79 were included in a subset for sequential semen sample analysis. The abstract reports no significant effects of 1 mg finasteride on sperm concentration, total sperm per ejaculate, sperm motility or morphology.
A 2013 study in Fertility and Sterility looked at men presenting to a male infertility clinic. It is an observational study, so it cannot show that finasteride caused any change. Of 4,400 men, 27 (0.6%) were on finasteride at presentation. The mean duration of treatment was 57.4 months and the mean dose was 1.04 mg/day. There was an average 11.6-fold increase in sperm counts after finasteride discontinuation. The authors concluded that finasteride, even at low doses, may cause reduced sperm counts in some men, and that in this population counts improved dramatically for the majority of men after discontinuation.
Studies of finasteride 5 mg and dutasteride
These results are not for the 1 mg tablet. The label states that two other studies showed finasteride at 5 times the dosage of Propecia (5 mg daily) produced significant median decreases of approximately 0.5 mL (-25%) compared to placebo in ejaculate volume, but this was reversible after discontinuation of treatment.
A 2007 randomized, double-blinded, placebo-controlled trial in 99 healthy men used dutasteride 0.5 mg (n = 33), finasteride 5 mg (n = 34), or placebo (n = 32) once daily for 1 year. Finasteride 5 mg is not the 1 mg hair-loss dose. Total sperm count compared with baseline was reported as follows:
| Time point | Change in total sperm count from baseline |
|---|---|
| 26 weeks | Significantly decreased: dutasteride 0.5 mg -28.6%; finasteride 5 mg -34.3%. |
| 52 weeks | Not significantly decreased: dutasteride 0.5 mg -24.9%; finasteride 5 mg -16.2%. |
| 24-week follow-up | Not significantly decreased: dutasteride 0.5 mg -23.3%; finasteride 5 mg -6.2%. |
The authors concluded that the decrease in DHT induced by 5ARIs (5-alpha-reductase inhibitors) is associated with mild decreases in semen parameters that appear reversible after discontinuation.
What this does not tell you
The studies used different doses, groups and lengths of time, so their results should not be added together. The 5 mg finasteride and dutasteride results do not show what happens at 1 mg.
The 1 mg trial reports no significant effects. The passage used here does not describe results for individual men, and it states the 60-week off-drug period without giving results from it. The clinic study is observational, was done in men presenting to an infertility clinic, and cannot show cause and effect.
Statements that semen measures improved or reversed after stopping come from different sources: the label's post-approval list, the label's 5 mg ejaculate volume statement, the clinic study, and the authors of the 5 mg and dutasteride trial. They are not one finding.
The passages used here report semen measures, not pregnancy or live-birth rates. A licensed provider can talk through these sources and a person's own circumstances.