Currently used in the treatment of alcohol and opioid addiction, acts as a competitive antagonist at opioid receptor sites, especially the μ receptors, which may be involved in the regulation of intestinal inflammation.

Competitive opioid antagonists bind to the opioid receptors with higher affinity than agonists, but  do not activate the receptors. 


It has a high affinity to mu opioid receptors.

It has a high affinity to mu opioid receptors.

Common dosing strategies for opioid use disorder includes 50 mg per day, and a typical daily dose will block the pharmacological effects of 25 mg of intravenous heroin for up to 24 hours.

Peak levels of naltrexone in its major metabolite are reached one hour after the first dose.

Displacing the agonist, attenuated  or reverses  the agonist effects. 

It has a longer duration of action, greater potency, and more oral bioavailability than naloxone.

Blockade of these receptors leads to increased endogenous opioid levels and also may block TNF-α synthesis.

Changes on immune function in the bowel is thought to be the basis of its effectiveness in Crohn’s disease.

Available in generic form and is administered once daily as a tablet.

Meta-analyses have shown that oral naltrexone is no more effective than placebo in lowering the rate of opioid use or increasing the rate of retention in treatment.

Injectable intramuscular naltrexone administered every 28 days is effective in reducing opioid cravings and elicit opioid use.

Prescribing injectable intramuscular naltrexone often requires prior authorization.

Initiation of oral or injectable naltrexone precipitates withdrawl symptoms if the patient has not abstained from opioid use for several days before initiation.

Naltrexone blocks mu-opioid receptors and the euphoric effects of opioids.

Compared with buprenorphine or methadone, naltrexone is not associated with a reduced risk of opioid-related or all-cause death.

In persons released from incarceration the administration of extended release naltrexone is associated with a more reduction in overdosing events.

Has no abuse potential, no street value, and is not associated with either tolerance or dependence.

It is thought to be relatively safe for long-term treatment of opioid use disorder, but can cause elevations and liver enzymes.

Naltrexone does not appear to increase risk of serious adverse events, which confirms its safety.

Mortality or serious adverse events due to rebound toxicity in patients with naloxone are rare..

Naltrexone may be administered in a monthly depot injection to control opioid abuse; in this case, the depot injection improves compliance by replacing daily pill administration.

Its use is associated with poor compliance with low adherence to the medication and poor retention in treatment.

It is dosed 50 mg by mouth once daily with 380 mg or by M injection once monthly.

Affects includes somnolence p, nausea vomiting, decreased appetite, abdominal pain, insomnia, and dizziness.

Side effects can be mitigated by taking the drug with food and building up the dose.

It blocks analgesic effects of opioids and can precipitate withdrawal from those who are opioid dependent.

Use should be avoided in patients with severe liver disease or those on chronic opioid pain medication.

It should be stopped  48 to 72 hours before surgery as perioperative management can be difficult for those using long acting naltrexone.


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