Simeprevir is a hepatitis C protease inhibitor used to treat chronic hepatitis C in combination with other medicines. It works by preventing the spread of the hepatitis C virus in the body. Do not use simeprevir if allergic to any ingredients, have severe liver problems, or are not also taking other drugs to treat hepatitis C infection. Simeprevir may interact with many other medications and herbal or dietary supplements, so be sure to discuss any other products you are taking with your doctor or pharmacist before using simeprevir. Carefully follow dosage instructions and continue treatment for the full prescribed period, even if symptoms improve, to avoid developing resistance to the medication.