Pentobarbital will decrease the level or effect of ketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. pentobarbital will decrease the level or effect of conjugated estrogens, vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. pentobarbital will decrease the level or effect of alosetron by affecting hep... https://bookmarkprobe.com/story20569121/i-pentobarbital-icp-diaries