phenobarbital increases toxicity of ifosfamide by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Check. CYP3A4 inducers may possibly improve the metabolism of ifosfamide to its Energetic alkylating metabolites.Check Intently (1)phenobarbital will decrease the level or result of tofacitinib by influencing hepatic/intestinal enz