What are the side effects of nalmefene?

You may have an allergic reaction to nalmefene requiring emergency medical attention. Symptoms of an allergic reaction include: itching, hives or skin rash; difficulty breathing; and swelling of your face, lips, tongue or throat. The following side effects associated with using nalmefene require prompt medical attention: extreme drowsiness; stomach cramps; weak or shallow breathing; chest pain or fluttering in your chest; pain that was controlled by narcotic pain medicine; high blood pressure; seizures; and feeling like you might pass out. Other side effects are generally minor and only require medical attention if they persist or disrupt your daily life. These include: nausea, vomiting, diarrhea and stomach pain; muscle or joint pain; fever, sweating or chills; runny nose; trembling; weakness; and feeling, irritable, anxious, restless or depressed.