pentobarbital will decrease the level or result of tamoxifen by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Use Warning/Keep an eye on.pentobarbital decreases amounts of elvitegravir/cobicistat/emtricitabine/tenofovir DF by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. May cause lack of virologic response and