- Concomitant use of drugs with a high probability of increasing the risk for hepatotoxicity or myopathy, such as those predominantly metabolized by cytochrome P450 system 3A4, including but not limited to cyclosporine, gemfibrozil, fenofibrate, itraconazole, ketoconazole, HIV protease inhibitors, nefazodone, verapamil, amiodarone; lipid-lowering drugs (other than the investigational drugs) such as statins, bile-acid sequestrants, cholesterol absorption inhibitors (e.g., ezetimibe), fibrates or high-dose, antioxidant vitamins (vitamins C, E, or beta carotene) that can interfere with the HDL-raising effect of niacin