Finasteride is not indicated for use by women. Finasteride is in the FDA pregnancy category X. This means that it is known to cause birth defects in an unborn baby. Women who are or who may become pregnant must not handle crushed or broken finasteride tablets, because the medication could be absorbed through the skin. Finasteride is known to cause birth defects in a developing male baby. Exposure to whole tablets should be avoided whenever possible, however exposure to whole tablets is not expected to be harmful as long as the tablets are not swallowed. It is not known whether finasteride passes into breast milk, and thus should not be taken by breastfeeding women. Finasteride may pass into the semen of men, but Merck states that a pregnant woman’s contact with the semen of a man taking finasteride is not an issue for concern.

Finasteride has been linked with depression. The drug also caused reductions in allopregnanolone, a potent, endogenous positive modulator of the GABA-A receptor, in very large doses in rodent studies.

Finasteride can also be used to mask steroid abuse, and many professional sports have banned finasteride use for this reason.

Finasteride is under investigation by the Swedish Medical Products Agency for possibly causing irreversible sexual side effects.