Naltrexone is an opioid-receptor antagonist used in the treatment of substance-use disorders. It is classified under Addiction Recovery medications and is supplied as a pill (tablet) in a 50 mg strength. In Hong Kong, naltrexone is a prescription-only product and is regulated by the Department of Health. Commercially, the active ingredient is marketed under several brand names, including Revia and Depade (oral tablets) and Vivitrol (injectable formulation).
Naltrexone binds competitively to μ (mu), κ (kappa) and δ (delta) opioid receptors in the central nervous system. By blocking these receptors, the medication prevents endogenous opioids (e.g., endorphins) and exogenous opioids (e.g., heroin, prescription pain relievers) from producing their usual rewarding effects. This antagonism reduces craving and helps maintain abstinence.
Key pharmacological points:
Naltrexone has received regulatory approval for the following indications:
In Hong Kong, these uses are reflected in the Product Registration Notice issued by the Department of Health. The medication is typically prescribed for adults who have achieved initial abstinence and are motivated to maintain recovery.
Research has explored additional applications of naltrexone, though they remain off-label in most jurisdictions, including Hong Kong:
These uses are not approved by regulatory agencies and should only be considered under close medical supervision, with a thorough risk-benefit assessment.
These effects are usually mild and transient, often resolving within the first week of therapy.
A black-box warning emphasizes the risk of liver damage; regular monitoring of liver function tests (LFTs) is recommended.
Patients should disclose all prescription, over-the-counter, and herbal products to their prescriber.
Note: Dosing must be individualized by a qualified healthcare professional; the above regimen reflects the most common prescription pattern for the 50 mg tablet.
This article provides educational information about naltrexone and is not a substitute for professional medical advice. Treatment decisions, including use for unapproved indications, must be made under the guidance of a qualified healthcare provider. The content is intended for informational purposes and does not constitute medical recommendations. Always consult a physician before starting, stopping, or changing any medication regimen.
Oral naltrexone tablets (50 mg) are taken once daily and are used mainly for alcohol dependence and for maintenance after opioid detoxification. The injectable form, Vivitrol, delivers 380 mg intramuscularly once a month and is often preferred for patients who have difficulty with daily adherence.
Naltrexone is most effective when the patient has already stopped drinking and is committed to abstinence. Starting the medication while still consuming alcohol may reduce its efficacy and increase the risk of side effects.
Patients typically notice a reduction in cravings within 1-2 weeks of consistent daily dosing, although individual response varies.
Mild to moderate liver impairment requires baseline and periodic liver function monitoring. The medication can be used cautiously, but severe hepatic disease is an absolute contraindication.
Naltrexone is a prescription medication; you should carry the original prescription or a doctor's letter when traveling, especially through customs in countries that require proof of medical necessity.
Non-opioid analgesics such as ibuprofen or acetaminophen do not interact with naltrexone and can be used as needed for mild pain.
This can precipitate acute withdrawal, which may cause severe nausea, vomiting, sweating, and agitation. Seek immediate medical attention; medical professionals can provide supportive care and, if necessary, administer short-acting opioid agonists under supervision.
There are no specific dietary restrictions, but taking the tablet with a small amount of food may lessen nausea. Avoid excessive alcohol, as it can strain the liver.
Initial testing before starting therapy, then every 4-6 weeks for the first three months, and subsequently as directed by your healthcare provider.
Combined therapy-such as counseling, support groups, or adjunct medications like acamprosate for alcohol dependence-can enhance overall treatment outcomes by addressing both physiological and behavioral aspects of addiction.
