Finasteride, a 5alpha-Reductase Inhibitor, Blocks the Anticonvulsant Activity of Progesterone in Mice

In the 1999 study, researchers found that progesterone, a hormone, had anticonvulsant effects against pentylenetetrazol (PTZ) seizures in mice. This effect was believed to be due to the conversion of progesterone to allopregnanolone, a neuroactive steroid, by 5alpha-reductase isoenzymes. The study showed that finasteride, a 5alpha-reductase inhibitor, could block the anticonvulsant activity of progesterone in a dose-dependent manner. However, finasteride did not affect the anticonvulsant activity of allopregnanolone itself or high doses of progesterone in the maximal electroshock seizure test. This provided strong evidence that the anticonvulsant effect of progesterone against PTZ-induced seizures was mediated by its active metabolite allopregnanolone.