pentobarbital will reduce the level or effect of saxagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Slight/Importance Not known.pentobarbital decreases amounts of elvitegravir/cobicistat/emtricitabine/tenofovir DF by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. May well cause loss of virologic reaction