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Naltrexone

Brands and Forms

  • ReVia
    • tablet: 50mg
  • Vivitrol
    • long-acting injectible suspension: 380mg/vial

Uses of Naltrexone

Naltrexone is used for preventing relapse in individuals who have recovered from alcohol or opioid abuse and dependence.

How Naltrexone Works

Naltrexone is a competitive antagonist at endogenous opioid receptors, and thus blocks the physiological effects of opioids and the euphoric effects of alcohol.

Cautions when Using Naltrexone

Naltrexone should not be used in people who remain dependent on opioids or are in acute opioid withdrawal. As a general rule, one should wait at least one week after a person has ceased all opioid use before starting Naltrexone, and Naltrexone should be stopped if signs and symptoms of opioid withdrawal appear.

Naltrexone should not be used in individuals suffering from acute hepatitis or liver failure.

Dosing of Naltrexone

Naltrexone is started at 50mg once daily, which is the also the maintenance dose. In individuals who have recently stopped opioid use, Naltrexone can be started at 25mg daily for a week while watching for any signs of opioid withdrawal, and thereafter the dose can be increased to 50mg daily.

Once a person has been found to tolerate Naltrexone for a period of at least a couple of weeks, the dose can be switched to the long-acting injectible form (Vivitrol), which is given at 380mg once every four weeks or every month. This form of the medication may produce better clinical results as it avoids the risk of the patient missing their daily doses and then experiencing the full effects of alcohol or opioids should they relapse into the substance use.

When wanting to stop Naltrexone, it can be discontinued immediately without the need for a gradual taper.

Onset of action

Naltrexone begins blocking the effects of opioids and alcohol after a single dose.

Kidney impairment

Use with caution in patients with moderate to severe renal function impairment.

Liver impairment

Naltrexone can contribute to liver impairment in should not be used in individuals who already have this condition.

Side-effects of Naltrexone

Below is a list of most of the reported side-effects of Naltrexone. Most of these side-effects occur in only a minority of individuals, and many also resolve with time while the medication is continued.

Central Nervous System: headache; dizziness; faintness; insomnia; sleep disorder; low or increased energy; loss of appetite; fatigue; sedation.

Dermatologic: skin rash.

Eyes, Ears, Nose and Throat: pharyngitis.

Gastrointestinal: nausea; dry mouth; abdominal pain; vomiting; diarrhea; abdominal cramps; increased thirst; constipation; elevated liver enzymes and liver impairment.

Genitourinary: erectile dysfunction; delayed ejaculation.

Muskuloskeletal: muscle and joint pain.

Psychiatric: depressed mood; anxiety; irritability; suicidal thoughts and behaviors.

Respiratory: Upper respiratory tract infection.

Common side-effects of Naltrexone

Headache, nausea, loss of appetite, dry mouth, abdominal pains, vomiting, diarrhea, dizziness, faintness, depressed and anxious moods, insomnia, pharyngitis, rash, muscle aches and pains, upper respiratory tract infection.

Rare but serious side-effects of note of Naltrexone

Liver impairment.

Naltrexone overdose

Abdominal pain, dizziness, nausea, somnolence.

Naltrexone and pregnancy

Category C: some animal studies show adverse effects at very high doses, but no controlled human studies have been done; should only be used in pregnancy if clearly needed and if benefits outweigh potential risks.

Medical Monitoring for Naltrexone

Measure liver enzyme levels before starting the medication and then a few weeks after starting, and then every 6 months to a year.

Drug Interactions with Naltrexone

  • Increased risk of liver impairment when combined with Disulfiram.
  • Do not administer to individuals receiving opioid medications.