You may not know for sure if someone is experiencing an opioid overdose. Treating the situation as a potential overdose with naloxone can prevent further serious injury or even death. If the person has not taken opioids, naloxone will not have an effect.

Side effects to naloxone are uncommon; however, allergic reactions to the medication are possible. Also, since the medicine only reverses the effects of opioids for 30 to 90 minutes, the person may still have overdose symptoms when naloxone wears off.

People who have developed physical dependence to opioids may experience withdrawal symptoms. These symptoms typically appear within minutes of giving naloxone. Symptoms include sweating, rapid heart rate, nausea, vomiting, restlessness and irritability. These symptoms are uncomfortable but not otherwise harmful to the person.