http://www.drugs.com/sfx/demerol-side-effects.html
Seek medical attention right away if any of these SEVERE side effects occur when using Demerol:
Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; difficulty urinating; fainting; fast, slow, or irregular heartbeat; mental or mood changes; numbness of an arm or a leg; seizure; severe or persistent dizziness; slowed or difficult breathing; sudden severe headache, nausea, vomiting, or stomach pain; tremor; vision changes.
