pentobarbital will decrease the level or effect of losartan by affecting hepatic enzyme CYP2C9/10 metabolism. Minor/Significance Unknown.pentobarbital increases effects of ifosfamide ort affecting hepatic enzyme CYP2B6 metabolism. Use Caution/Monitor. Coadministration of ifosfamide with CYP2B6 inducers may increase metabolism of ifosfamide to its m