Because of its fast onset (minutes), naloxone (Narcan) administered IV is used most frequently for the reversal of opioid overdose. However, it fails to block some side effects of the opioids that are mediated by the ct-receptor, such as hallucinations. The rapid offset of naloxone makes it necessary to administer the drug repeatedly until the opioid agonist has cleared the system to prevent relapse into overdose. The half-life of nalox-one in plasma is 1 hour. It is rapidly metabolized via glucuronidation in the liver and cleared by the kidney. Naloxone given orally has a large first-pass effect, which reduces its potency significantly. Often an overshoot will follow the administration of naloxone for overdose. The heart rate and blood pressure of the patient may rise significantly. The overshoot is thought to be due to precipitation of acute withdrawal signs by naloxone. Given alone to nonaddicts, naloxone produces no pharmacological effects.
Naloxone is approved for use in neonates to reverse respiratory depression induced by maternal opioid use. In addition, naloxone has been used to improve circulation in patients in shock, an effect related to blockade of endogenous opioids. Other experimental and less well documented uses for naloxone include reversal of coma in alcohol overdose, appetite suppression, and alleviation of dementia from schizophrenia. Side effects of naloxone are minor.
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