pentobarbital increases toxicity of ifosfamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Warning/Check. CYP3A4 inducers could boost the metabolism of ifosfamide to its Energetic alkylating metabolites. pentobarbital will lessen the extent or outcome of vardenafil by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Use C