Excessive doses or rapid intravenous administration may produce additional methemoglobinemia. Hemolysis, precordial pain, nausea, dizziness, headache and profuse sweating have been reported. Narcan Naloxone, an opioid antagonist devoid of agonistic effects, is a competitive antagonist at all opioid receptor sites. Respiratory depression, coma and seizures associated with opioid poisoning are rapidly reversed by naloxone. Since naloxone does not depress the central nervous system and does not antagonize other CNS depressants such as barbituates, benzodiazepines, or alcohol, it is a safe diagnostic agent to rule out opioid poisoning in comatose patients with unknown drug ingestions.
Naloxone is nontoxic even in doses ten to twenty times larger than recommended doses.
Although narcotic withdrawal symptoms are likely to occur in patients physically dependent to opioids, the symptoms last for fifteen to thirty minutes after a recommended dose and usually do not interfere with patient management. The usual naloxone dose is 0.4 mg to 2 mg in children and adults given as an intravenous bolus. Clinical response occurs within two to three minutes. Additional doses should be given at two to three minute intervals as needed to reverse coma and cardiopulmonary depression. Patients who have overdosed with buprenorphine, propoxyphene, pentazocine or large doses of opioids may require naloxone doses as large as 0.1 mg per Kg or greater.