pentobarbital increases toxicity of ifosfamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Warning/Observe. CYP3A4 inducers may boost the metabolism of ifosfamide to its active alkylating metabolites.pentobarbital will decrease the extent or effect of triazolam by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Use Cautio