Naltrexone
Naltrexone is a medication primarily used to treat alcohol use disorder (AUD) and opiate use disorder (OUD). As an opioid receptor antagonist, it binds to the mu opioid receptors in the brain without activating them, which helps reduce cravings and prevents the euphoric effects associated with alcohol and opioids. This mechanism makes naltrexone a useful adjunct to psychosocial therapies for addiction treatment. In addition to its use in addiction, naltrexone is combined with bupropion in a medication called Contrave, which is approved for weight loss in individuals who are overweight or obese with related health conditions. Naltrexone is available in oral form (ReVia or Depade) and as an intramuscular injection (Vivitrol), with the injection generally having fewer side effects. While naltrexone has shown positive outcomes in reducing heavy drinking and enhancing treatment compliance, some patients may experience side effects like nausea and headaches. Importantly, naltrexone should not be administered to individuals with active liver disease or those currently using opioids, as it can induce withdrawal symptoms. Overall, naltrexone plays a significant role in the management of substance use disorders and obesity, offering a valuable option for many patients.
Naltrexone
ALSO KNOWN AS: Naltrexone hydrochloride; ReVia; Depade; Vivitrol
DEFINITION: Naltrexone is a medication prescribed for the treatment of alcohol use disorder (AUD) and opiate use disorder (OUD). It has also been utilized in combination with bupropion to assist in weight loss.
How Does Naltrexone Work?
Naltrexone is an antagonist that binds to the mu (µ) opioid receptors in the brain but does not stimulate them. This is important because naltrexone is used to treat addictions and use disorders, but like other addiction medications, it does not result in euphoria. When used with psychosocial therapy, naltrexone has been shown to be an effective adjunct for the treatment of addiction disorders.
Once naltrexone has reached a therapeutic level in the patient’s system (in as little as a few hours), a couple of processes occur. First, there is typically a significant drop in cravings for the drug, and second, if opiates (such as heroin, morphine, and buprenorphine) or alcohol are used, no euphoria is experienced. Naltrexone blocks the activation of the receptors of the dopamine that is typically released when opiates or alcohol are consumed: No dopamine means no euphoria.
Furthermore, because these receptors are accustomed to being stimulated, a lack of dopamine results in more cravings. With naltrexone occupying those receptors, cravings decrease significantly. The decrease in cravings, coupled with the loss of the euphoria experienced when drinking or using opiates, may dramatically reduce the chances of relapse and provide the patient with the extra assistance needed to participate in psychosocial treatment or discontinue use of the substance. It must be noted that because naltrexone will remove any chemical currently occupying the receptor, symptoms of withdrawal will follow. Because of this, the patient must be free of opiates before being given naltrexone.
In March 2010, Orexigen Therapeutics submitted an application to the US Food and Drug Administration for the approval of their drug Contrave, which is a combination of naltrexone and bupropion, for weight loss. In September 2014, the FDA approved the use of Contrave and the drug has been widely used ever since. It is meant for people who are overweight or obese and have at least one weight-related condition, such as type-2 diabetes, hypertension, or dyslipidemia. The drug acts similarly for over-weight or obese people as it does for individuals with AUD or OUDit inhibits the parts of the brain that signal hunger and cravings, quieting the often constant urge for food. It also lessens the appeal, or euphoria, of food, which makes consumers less likely to binge or stress eat.
Side effects of naltrexoneinclude nausea, headache, dizziness, anxiety, fatigue, and trouble sleeping. Hepatotoxicity, or chemical-induced liver damage, has been found when naltrexone is given in excessive doses. The specificity and intensity of the side effects may depend on the form in which the medication is taken.
Drug Forms
Naltrexone is prescribed in two different forms—oral (ReVia or Depade) and in an intramuscular injection (Vivitrol). ReVia is typically prescribed in a 50 milligram dose, once daily. Reactions to oral naltrexone vary. Some patients have reported side effects severe enough to discontinue use. However, frequency of side effects is greatly reduced with the once-monthly injectable form of naltrexone, Vivitrol. It can also be administered via a slow-release injection in a 380 mg dose.
Contrave is administered in pill form, which gradually increases overtime. Patients typically start out taking one pill (8mg naltrexone/90 mg bupropion) once daily but then progress in week two by taking one pill in the morning and one in the night. Weeks three through four also see progressive dosing as long as no harmful side effects appear.
Efficacy
Naltrexone has been shown to have positive, albeit varied results. Some research indicates that patients on naltrexone report significant reductions in their average and heavy drinking days (more than four to five drinks per day). Other research for AUD and OUD patients indicates positive treatment outcomes in the areas of retention, compliance, and group therapy attendance. However, other studies report some problems with medication adherence. However, for patients using Contrave for weight loss, results are more promising as many studies have shown that patients who take Contrave experience greater weightloss overtime than those who take a placebo or take nothing.
Contraindications
Naltrexone in either form (oral or injection) is contraindicated for anyone with active hepatitis, liver failure, or severe liver disease. In addition, anyone who is actively taking opiates (either illicitly or for pain) should not take naltrexone because it will negate any opiate-based effects (for example, pain reduction or management). Additional contraindications may depend on the form of the medication.
Bibliography
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Sherman, Matthew M., et al. “Naltrexone/Bupropion ER (Contrave): Newly Approved Treatment Option for Chronic Weight Management in Obese Adults.” P & T 41.3 (2016): 164-72. Accessed 27 Aug. 2024.
Singh, Dharminder, and Abdolreza Saadabadi. "Naltrexone." StatPearls, 30 May 2023, www.ncbi.nlm.nih.gov/books/NBK534811/. Accessed 27 Aug. 2024.
“What Is Naltrexone? Side Effects, Uses, Dose & Risk.” Substance Abuse and Mental Health Service Administration, 29 Mar. 2024, www.samhsa.gov/medications-substance-use-disorders/medications-counseling-related-conditions/naltrexone. Accessed 27 Aug. 2024.