pentobarbital will minimize the level or effect of exemestane by impacting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Watch. For individuals getting exemestane with a strong CYP3A4 inducer the encouraged dose of exemestane is 50 mg day-to-day after a meal.pentobarbital increases effects of ifosfamide by affecting hepatic enzyme CYP2B6