Butabarbital will minimize the extent or result of levonorgestrel oral/ethinylestradiol/ferrous bisglycinate by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Carefully. The efficacy of hormonal contraceptives may very well be decreased. butabarbital will lessen the level or influence of vardenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism... https://johnq086nxz9.wannawiki.com/user