From the Guidelines
Naltrexone is an opioid antagonist that blocks the effects of opioid agonists and is used to treat opioid dependence and alcohol dependence. It is available in a 50-mg tablet taken daily or a 380-mg monthly injection (Vivitrol) 1. Naltrexone works by preventing the impulsive use of opioids in patients and providing time for them to consider the consequences of relapse and seek support.
Key Points about Naltrexone
- Naltrexone is an antagonist of mu opioid receptors, which can prevent the euphoric effects of opioids and reduce cravings 1.
- It is available as a 50-mg tablet taken daily or, alternatively, 100 mg on Mondays and Wednesdays, and 150 mg on Fridays, as well as a 380-mg monthly injection (Vivitrol) 1.
- Naltrexone has been shown to be helpful in maintaining abstinence from opioids in motivated populations, such as healthcare professionals who cannot or do not wish to take continuous opioid agonist therapy 1.
- However, it has had limited success in other groups and can be associated with hepatic injury at supratherapeutic doses, requiring liver function tests at baseline and every three to six months 1.
- Naltrexone cannot be used in patients in whom opioids are required for pain control, because it will block pain relief from opioid agonists and cause withdrawal symptoms.
Important Considerations
- Patients must be fully detoxified from opioids before starting naltrexone to avoid precipitating severe withdrawal symptoms.
- Common side effects of naltrexone include nausea, headache, dizziness, anxiety, and fatigue.
- It is essential for patients to inform all healthcare providers they're taking naltrexone and wear medical identification in case emergency pain treatment is needed.
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. Naltrexone hydrochloride, an opioid receptor antagonist, competitively binds to such receptors and may block the effects of endogenous opioids Naltrexone hydrochloride is a synthetic congener of oxymorphone with no opioid agonist properties.
Naltrexone is a pure opioid antagonist, which means it blocks the effects of opioids by competitively binding to opioid receptors. It is used to treat opioid dependence and alcoholism. 2 2
- Key characteristics:
- Pure opioid antagonist
- Blocks effects of opioids
- No opioid agonist properties
- Used to treat opioid dependence and alcoholism
From the Research
Definition and Mechanism of Naltrexone
- Naltrexone is an opioid receptor antagonist that blocks the reinforcing effects of opioids and reduces alcohol consumption and craving 3, 4, 5.
- It works by blocking the opioid receptors that modulate the release of dopamine in the brain reward system, thereby blocking the rewarding effects of heroin and alcohol 3, 6.
Uses of Naltrexone
- Naltrexone is used to treat opioid and alcohol dependence 3, 4, 5, 7.
- It is also used to reduce alcohol craving and alcohol use in patients with alcohol dependence 4, 7.
- Naltrexone has been shown to be effective in reducing heroin use in opioid-dependent patients 3.
Administration and Formulations
- Naltrexone is available in oral, implant, and injectable depot formulations 3, 5.
- The injectable formulation provides naltrexone release for at least 1 month, while implant formulations can release naltrexone for up to 7 months 3.
- A long-acting injectable formulation of naltrexone has received FDA-approval for treating alcohol and opioid dependence 5.
Safety and Efficacy
- Naltrexone has been shown to be safe and well-tolerated, with mild and transient side effects 3, 4.
- However, it can precipitate narcotic withdrawal in patients taking narcotics, and hepatotoxicity can occur at high dosages 4.
- The efficacy of naltrexone in reducing craving and alcohol use has been demonstrated in several studies, but the results are sometimes inconsistent 3, 4, 7, 6.