phenobarbital raises toxicity of ifosfamide by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Observe. CYP3A4 inducers may well enhance the metabolism of ifosfamide to its Energetic alkylating metabolites.Observe Closely (1)somatropin will reduce the extent or influence of phenobarbital by impacting hepatic/intestinal enzyme C