Naloxone action

Administration of naloxone prevents or reverses the effects of the opiates. The exact mechanism of action is not fully understood, but it is believed that naloxone reverses opioid effects by competing for opiate receptor sites (see Chap. 19). If the individual has taken or received an opiate, the effects of the opiate are reversed. 

These dm may produce withdrawal symptoms in those physically dependent on the narcotics. The patient must not have taken any opiate for the last 7 to 10 days. Naloxone may prevent die action of opioid antidiarrheals, antitussives, and analgesics. This drug is used cautiously during lactation. 

Naltrexone completely blocks the effects of IV opiates, as well as drugp with agonist-antagonist actions (butorphanol, nalbuphine, and pentazocine). The mechanism of action appears to be the same as that for naloxone... 

The opioid antagonists naloxone and naltrexone bind to aU three opioid receptors, p, K, and 8. These compounds are antagonists due to their inability to elicit downstream effects of these receptors once bound (Sarton et al. 2008 Yaksh and Rudy 1977). Interestingly, both antagonists have a high binding affinity for MORs. Naloxone is used to reverse the effects of an acute opioid overdose because of its rapid onset of action. Naltrexone elicits similar actions, but has a longer onset and duration of action and hence, is used for the maintenance of treatment for opioid addicts. 

The intoxicating effects of opioids appear to be due to their action as agonists on mu (p) receptors of the opioid neurotransmitter system. Competitive p opioid antagonists such as naloxone and naltrexone acutely reverse many of the adverse effects of opioids. To date we do not have specific antagonists for most other abused substances, so rapid pharmacologic reversal of intoxication is usually not possible. 

In electrophysiological studies aimed at elucidating the mechanism of action of kappa agonists, U-50488 has been shown to depress excitatory post-synaptic potentials in a rat locus coeruleus preparation, which indicates that it acts presynaptically to inhibit transmitter release [38]. Also, in spinal cord slice preparations from the 9-16-day-old rat, U-69593 (9) produced a naloxone-reversible depression of spontaneous and electrically evoked activity in dorsal horn neurones [39],... 

Naloxone (75) is an opioid antagonist with slightly higher affinity for the mu subtype than kappa (A) in guinea-pig brain mu = 1.78 nM kappa = 27 nM delta = 1.72 nM) [96] and is widely used as a pharmacological tool to demonstrate the mechanism of action of opioid agonists. Despite much... 

Only one antagonist is known, naloxone, which is used clinically to treat opiate overdoses and, experimentally, to investigate whether physiological or biochemical actions are opiate-mediated. One example of its use is to support the hypothesis that P-endorphin is responsible for the analgesic effects of acupuncture. Not only does low frequency electroacupuncture increase p-endorphin levels in cerebrospinal fluid but naloxone nullifies the analgesic effect of this treatment. 

Naloxone has been used for the treatment of dependence on heroin and has the advantage of potency, rapid action, absence of side-effects, and acceptability on the debit side are its brief action and high cost [228]. 

It is worth mentioning that iV-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.Synonyms for this drug are narkan, talwin, and others. 

Respiratory depression Accidental overdose with long-acting opioids (eg, methadone, levomethadyl) may result in prolonged respiratory depression. While nalmefene has a longer duration of action than naloxone in fully reversing doses, be aware that a recurrence of respiratory depression is possible. Observe patients until there is no reasonable risk of recurrent respiratory depression. 

Onset, peak, and duration - Onset of action of IV naloxone is generally apparent within 2 minutes it is only slightly less rapid when given subcutaneously or IM. Duration of action of 1 to 4 hours depends upon dose and route. IM use produces a more prolonged effect than IV use. 

Respiratory depression caused by opioid analgesics can be reversed by opioid antagonists, such as naloxone. Because the duration of respiratory depression may last longer than the duration of the opioid antagonist action, maintain appropriate surveillance. 

Meperidine (Demerol) [C-ll] [Narcotic Analgesic] Uses Moderate/ severe pain Action Narcotic analgesic Dose Adults. 25-50 mg IV, 50-100 mg IM Peds. 1 mg/kg IV/IM (onset w/in 5 min IV and 10 min IM duration about 2 h) Caution [C, ] Contra Convulsive disorders and acute abdomen Disp Prefilled 1 mL syringes 25, 50, 75, 100 mg/mL various amps and vials oral syrup and tabs SE N/V (may be severe), dizziness, weakness, sedation, miosis, resp d ession, xerostomia (dry mouth) Interactions t CNS depression W/ opiates, sedatives/ hypnotics TCNS stimulation W/amphetamines t risk of tox W7 phenytoin EMS Pt should be receiving O2 prior to administration have resuscitation equipment and naloxone available naloxone can be used as an antidote to reverse resp depression aspirate prior to IM administration inadv tent IV admin of IM doses may cause tach and syncope mix w/ NS to make a 10 mg/mL soln and inj very slowly N/V may be sev e may premedicate w/ an antiemetic... 

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