pentobarbital will lessen the extent or influence of ketoconazole by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Minimal/Importance Not known.pentobarbital will lower the extent or influence of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Observe Closely. Solid or reasonable CYP3A4 inducers noticeab