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 quinine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. When barbiturates like Nembutal are abused, they are not usually the primary drug of abuse. ... https://socialtechnet.com/story5817493/poco-conosciuto-fatti-circa-pentobarbital-natrium