Butabarbital will decrease the level or effect of levonorgestrel oral/ethinylestradiol/ferrous bisglycinate by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Keep an eye on Carefully. The efficacy of hormonal contraceptives might be decreased. butabarbital will decrease the level or result of vardenafil by impacting hepatic/intestinal enzyme CYP3A4 metabolism.... https://helenp998zgn5.wikifrontier.com/user