Some medicines can interact with ISENTRESS and ISENTRESS HD. Tell your doctor if you take antacids containing aluminum, magnesium, or calcium; rifampin; tipranavir/ritonavir; etravirine; or other drugs such as carbamazepine, phenobarbital, and phenytoin. It is not recommended to take these medicines with ISENTRESS or ISENTRESS HD. Your doctor will tell you if it’s safe to take ISENTRESS or ISENTRESS HD with other medicines.