pentobarbital boosts toxicity of ifosfamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Warning/Watch. CYP3A4 inducers may possibly enhance the metabolism of ifosfamide to its Energetic alkylating metabolites.pentobarbital will lower the level or result of etonogestrel by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Us