phenobarbital improves toxicity of ifosfamide by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Use Warning/Keep track of. CYP3A4 inducers might improve the metabolism of ifosfamide to its Lively alkylating metabolites.Phenobarbital is a barbituric acid by-product for oral administration and happens as a white, odorless, a little bit bitter