Ketoconazole is a strong CYP3A4 inhibitor, which means it slows down the way your body breaks down Levomilnacipran. As a result, more of the medicine stays in your body. So when you take the two together, the daily dose of Levomilnacipran should not go above 80 mg, taken once a day.
These medicines are often taken together with some care. Your doctor may change a dose, space them apart or check on you more often. Make sure your doctor and pharmacist know you take both.