pentobarbital will lower the level or impact of tramadol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Check. Decreased AUC of tramadol and the Lively metabolite (O-desmethyltramadol) when coadministered with strong CYP3A4 and CYP2B6 inducerspentobarbital raises toxicity of ifosfamide by affecting hepatic/intestinal enzyme C