mavacamten will decrease the level or influence of ethinylestradiol by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Progestin and ethinyl estradiol are CYP3A4 substrates. Mavacamten may lessen systemic exposures of ethinyl estradiol and progestin, which may result in contraceptive failure or a rise in breakthr