Налоксон

Описание

It is worth mentioning that N-allylic substitution in a number of morphine derivatives, as a rule, leads to antagonistic properties. Naloxone is a few times stronger than nalorphine as an antagonist. It blocks opiate receptors. It eliminates central and peripheral action of opioids, including respiratory depression. Naloxone is used upon overdose of narcotic analgesics.

Использование

Naloxone is a specific opioid antagonist. Narcotic antagonist.

Определение

ChEBI: A synthetic morphinane alkaloid that is morphinone in which the enone double bond has been reduced to a single bond, the hydrogen at position 14 has been replaced by a hydroxy group, and the methyl group attached to the nitrogen has been replaced by an all l group. A specific opioid antagonist, it is used (commonly as its hydrochloride salt) to reverse the effects of opioids, both following their use of opioids during surgery and in cases of known or suspected opioid overdose.

Биологические функции

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 δ- 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 naloxone 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.

Общее описание

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.