Naloxone

Use

Naloxone (Narcan) is a pure antagonist at allopioid receptor subtypes. Structurally, it resembles oxymorphoneexcept that the methyl group on the nitrogen isreplaced by an allyl group. This minor structural change retains high binding affinity to the receptor, but no intrinsicactivity. It is used to reverse the respiratory depressant effectsof opioid overdoses.Naloxone is administered intravenously with an onset ofaction within 2 minutes. Because it is competing with theopioid for the receptor sites, the dose and frequency of administrationwill depend on the amount and type of narcoticbeing antagonized. Overdoses of long-acting opioids(methadone) may require multiple IV doses of naloxone orcontinuous infusions. Neonates born to opioid-exposedmothers may be given IV naloxone at birth to reverse the effectsof opiates.Very few metabolism studies on naloxone have beenconducted, although the major metabolite found in the urineis naloxone-3-glucuronide.