What is the use of Naltrexone (opioid receptor antagonist)?

From the Guidelines

Naltrexone is a medication used to treat opioid addiction and alcohol dependence by blocking opioid receptors, and its use should be prioritized in motivated populations, such as healthcare professionals, due to its effectiveness in maintaining abstinence from opioids 1.

Key Points

• Naltrexone is available as a 50-mg tablet taken daily or, alternatively, 100 mg on Mondays and Wednesdays, and 150 mg on Fridays, and a 380-mg monthly injection (Vivitrol) is also available 1.
• Patients must be opioid-free for a certain period before starting Naltrexone to avoid precipitating withdrawal, and liver function tests are recommended at baseline and every three to six months due to the risk of hepatic injury at supratherapeutic doses 1.
• Naltrexone has been shown to be helpful in maintaining abstinence from opioids in motivated populations, but has had limited success in other groups, and its use should be considered in combination with counseling or behavioral therapy 1.
• The medication works by blocking opioid receptors, reducing the euphoric effects of opioids and decreasing alcohol cravings, and common side effects include nausea, headache, and fatigue 1.

Clinical Considerations

• It's crucial to inform healthcare providers about Naltrexone use before any medical procedures, as it can interfere with opioid pain medications, and patients should carry a medical alert card, as Naltrexone can block the effects of opioid pain medications in emergencies 1.
• Naltrexone is not addictive and doesn't cause withdrawal when stopped, but abruptly discontinuing may increase opioid sensitivity, and its use should be carefully considered in patients with a history of opioid use disorder 1.
• Recent studies have found that oral or long-acting injectable formulations of naltrexone can be used as medication-assisted treatment for opioid use disorder in nonpregnant adults, particularly for highly motivated persons 1.

From the FDA Drug Label

Naltrexone hydrochloride is a pure opioid antagonist. It markedly attenuates or completely blocks, reversibly, the subjective effects of intravenously administered opioids. The mechanism of action of naltrexone hydrochloride in alcoholism is not understood; however, involvement of the endogenous opioid system is suggested by preclinical data. Naltrexone hydrochloride, an opioid receptor antagonist, competitively binds to such receptors and may block the effects of endogenous opioids

The use of Naltrexone is as an opioid receptor antagonist to:

• Block the effects of opioids by competitive binding at opioid receptors
• Aid in the treatment of alcoholism by reducing alcohol consumption
• Block the physical dependence to morphine, heroin, and other opioids 2, 2, 2

From the Research

Use of Naltrexone

• Naltrexone is a broad opioid-receptor antagonist used in the management of alcohol dependence 3, 4, 5, 6.
• It is effective in reducing relapse to heavy drinking, but less effective in enhancing abstinence 3.
• Naltrexone works by blocking the pleasurable effects or "high" associated with alcohol drinking, thereby reducing alcohol craving and use 4, 5, 6.
• The therapeutic effects of naltrexone are mediated by blockade of central mu opioid receptors, particularly in the central nucleus of the amygdala, nucleus accumbens, and ventral tegmental area 6.

Administration and Efficacy

• Naltrexone can be administered orally or through injectable extended-release formulations 3, 7.
• Oral naltrexone has been shown to reduce relapse and heavy drinking in alcohol-dependent patients, but is associated with poor compliance and adverse events 7.
• Injectable extended-release naltrexone formulations have been developed to enhance treatment outcome and reduce side effects, but more studies are needed to compare their efficacy with oral naltrexone 7.

Safety and Tolerability

• The most common adverse effects reported with the use of naltrexone include nausea and vomiting 3, 4, 5.
• Naltrexone does not appear to be hepatotoxic in dosages recommended in the treatment of alcohol dependence (50 mg/day) 3, 4, 5.
• However, hepatotoxicity can occur at higher doses, and naltrexone can precipitate narcotic withdrawal in patients taking narcotics 5.