pounding heartbeat, seizure (black-out or convulsions); pale skin, feeling light-headed or short of breath, rapid heart rate, overactive reflexes, nausea, vomiting, diarrhea, drowsiness, muscle weakness, tightness, or contraction, overactive reflexes; very stiff (rigid) muscles, high fever, sweating, confusion, fast or uneven heartbeats; pain or heavy sweating can cause a sudden and severe dizziness, fainting, fast or pounding heartbeats, feeling like you might pass out; headache, trouble concentrating, memory problems, weakness, feeling unsteady, loss of appetite); unusual or bothersome side effect. You may report side to