butabarbital will reduce the extent or influence of sulfamethoxazole by impacting hepatic enzyme CYP2C9/ten metabolism. Minimal/Importance Unidentified.butabarbital will decrease the level or impact of conivaptan by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Watch.butabarbital will lessen the level or outcome of pimozide by