pentobarbital will lower the level or influence of fludrocortisone by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.pentobarbital will lower the level or impact of tramadol by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Use Warning/Watch. Lowered AUC of tramadol and also the active metabolite (O-desmethyltram