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Naloxone
Opioid receptor antagonist / From Wikipedia, the free encyclopedia
Naloxone, the active ingredient in Narcan, is an opioid antagonist: a medication used to reverse or reduce the effects of opioids.[13] Naloxone is commonly used to restore breathing after an opioid overdose.[13] Effects begin within two minutes when given intravenously, five minutes when injected into a muscle,[13] and ten minutes as a nasal spray.[14] Naloxone blocks the effects of opioids for 30 to 90 minutes.[15]
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Trade names | Narcan, Evzio, Nyxoid, others |
Other names | EN-1530; N-Allylnoroxymorphone; 17-Allyl-4,5α-epoxy-3,14-dihydroxymorphinan-6-one, naloxone hydrochloride (USAN US) |
AHFS/Drugs.com | Monograph |
MedlinePlus | a612022 |
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Routes of administration | Nasal, intravenous, intramuscular |
Drug class | Opioid antagonist |
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Bioavailability | 2% (by mouth, 90% absorption but high first-pass metabolism) 43–54% (intranasally) 98% (intramuscular, subcutaneous)[12][13] |
Metabolism | Liver |
Onset of action | 2 min (IVTooltip intravenous injection), 5 min (IMTooltip intramuscular injection)[13] |
Elimination half-life | 1–1.5 h |
Duration of action | 30–60 min[13] |
Excretion | Urine, bile |
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ECHA InfoCard | 100.006.697 ![]() |
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Formula | C19H21NO4 |
Molar mass | 327.380 g·mol−1 |
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Administration to opioid-dependent individuals may cause symptoms of opioid withdrawal, including restlessness, agitation, nausea, vomiting, a fast heart rate, and sweating.[13] To prevent this, small doses every few minutes can be given until the desired effect is reached.[13] In those with previous heart disease or taking medications that negatively affect the heart, further heart problems have occurred.[13] It appears to be safe in pregnancy, after having been given to a limited number of women.[16] Naloxone is a non-selective and competitive opioid receptor antagonist.[6][17] It works by reversing the depression of the central nervous system and respiratory system caused by opioids.[13]
Naloxone was patented in 1961 and approved for opioid overdose in the United States in 1971.[18][19] It is on the World Health Organization's List of Essential Medicines.[20] Naloxone is available as a generic medication.[13][21]