Possible Interaction: Progesterone and Finasteride

“Blocking progesterone ’s metabolism to 5α -pregnan-3α -ol-20-one (3α ,5α -THP) with finasteride , a 5α -reductase inhibitor, and effects on anxiolytic, exploratory, and antinociceptive behaviors of rats in behavioral estrus were examined.”

“Finally, finasteride did not only affect, as expected, the levels of 5alpha-reduced metabolites of progesterone and testosterone, but also the further metabolites and precursors suggesting that this drug has broad consequence on neuroactive steroid levels of PFS patients.”

“Due to the capability of finasteride to block the metabolism of progesterone (PROG) and/or testosterone (T) we have evaluated, by liquid chromatography-tandem mass spectrometry, the levels of several neuroactive steroids in paired plasma and cerebrospinal fluid (CSF) samples obtained from post-finasteride patients and in healthy controls.”

“ Finasteride treatment resulted in a significant decrease all alpha-reduced and increase of most 5beta-reduced metabolites of testosterone and progesterone as well as in an increase of 7alpha-hydoxyderivatives, which are known as neuroactive steroids acting by modulation of GABAA and NMAD receptors in the brain.”

“Even 1 nM finasteride inhibited DHT synthesis in DP by 86% and 1 nM progesterone by 75%.”

“Inhibition of steroid 5alpha-reductase with finasteride completely blocked metabolism of progesterone but had no effect on inhibition of LDL-stimulated cholesterol esterification (IC50 = 10 microM).”

“The protective effect of progesterone was abolished in the presence of finasteride , a 5α-reductase inhibitor, suggesting it was largely mediated via its conversion to allopregnanolone.”

“ Finasteride inhibited 5alpha-reduced progesterone metabolism but did not impact serum progesterone concentrations in these ewes.”

“While the neuroprotection conferred by progesterone was not affected by SU-10603, an inhibitor of cytochrome P45017α, finasteride , a 5α-reductase inhibitor that blocks the conversion of progesterone to allopregnanolone, partially reversed the neuroprotection induced by progesterone.”

“Prior administration of finasteride decreased allopregnanolone concentrations and abolished the increase in proceptivity induced by progesterone administration.”