Get emergency medical help if you have signs of an allergic reaction to naloxone: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Because naloxone reverses opioid effects, administration may cause sudden withdrawal symptoms such as:
nausea, vomiting, diarrhea, stomach pain;
fever, sweating, body aches, weakness;
tremors or shivering, fast heart rate, pounding heartbeats, increased blood pressure;
goose bumps, shivering;
runny nose, yawning; or
feeling nervous, restless, or irritable.
Sudden withdrawal symptoms in a baby younger than 4 weeks old may be life-threatening if not treated the right way. Symptoms include crying, stiffness, overactive reflexes, and seizures. Call your doctor or get emergency medical help if you are not sure how to properly give this medicine to a baby.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Naloxone side effects (more detail)
