-Kirk Tjalas, F.N.P.

Kirk Tjalas, F.N.P., provides exceptional care and meticulous attention to detail for every patient concern, ensuring comprehensive and personalized treatment for optimal health outcomes.

Medical Consultation

Every year, millions of Americans struggle with opioid and alcohol use disorders conditions that are not failures of willpower but complex, neurobiological diseases that respond to medical treatment. And yet, one of the most effective medications available for both conditions remains dramatically underutilized. According to the American Journal of Psychiatry, prescribing naltrexone for alcohol misuse continues to be “one of the most underutilized interventions in medicine” despite decades of clinical evidence. That gap between evidence and practice costs lives and patients.

Naltrexone is an FDA approved opioid antagonist used to treat opioid use disorder (OUD) and alcohol use disorder (AUD). The World Health Organization estimates that over 75 million people worldwide meet criteria for alcohol use disorder or dependence a staggering public health burden that evidence based medications like naltrexone are positioned to address. More recently, naltrexone has gained attention for a second role: when combined with bupropion in the medication Contrave, it is FDA approved as a weight management tool. Understanding how naltrexone works, who it helps, and what to realistically expect from it can empower patients and their families to make better informed decisions about care.

How Naltrexone Works: The Science in Plain Language

Naltrexone was first synthesized in the 1960s and received FDA approval in 1984 for opioid use disorder and in 1994 for alcohol use disorder. To understand why it works, you need to understand what it does in the brain.

The brain has a network of opioid receptors particularly mu, kappa, and delta receptors that respond to the body’s natural endorphins as well as to external opioids and alcohol. When someone uses heroin, morphine, or drinks heavily, these receptors are activated, producing the euphoria and reward sensation that reinforces continued use.

Naltrexone is an opioid antagonist meaning it binds tightly to those same opioid receptors and blocks them, without activating them. The result:

Opioids cannot produce their characteristic euphoric or sedating effects
Alcohol’s reward producing mechanism is blunted significantly
Cravings diminish over time, because the brain’s reinforcement cycle is interrupted

Critically, naltrexone is neither an opioid nor a controlled substance. It is not addictive, has no intoxicating effects, and produces no “high.” According to SAMHSA, it can be prescribed by any licensed practitioner with prescribing authority unlike methadone and buprenorphine, which carry additional regulatory requirements.

Naltrexone is available in two FDA approved forms:

Oral tablet (50 mg daily): Typically used for alcohol use disorder, taken once daily
Extended release injectable (Vivitrol, 380 mg monthly): Approved for both AUD and OUD; administered by a healthcare provider every four weeks, removing the daily adherence burden

Naltrexone for Opioid Use Disorder

For opioid use disorder, naltrexone offers a meaningful advantage in certain patient contexts: unlike methadone (a full opioid agonist) or buprenorphine (a partial agonist), naltrexone carries no abuse potential and no risk of diversion. Patients cannot misuse it to get high.

The extended release injectable formulation (Vivitrol) is particularly important here. Because oral naltrexone adherence rates have historically been low it is difficult to sustain daily oral dosing for a condition defined in part by impulsivity a once monthly injection addresses the adherence problem directly. FDA approved Vivitrol for OUD prevention of relapse in 2010, and it has become an important option for patients completing medically supervised opioid withdrawal.

Critical safety point: Patients must be fully opioid free for 7 to 14 days before starting naltrexone. Beginning the medication while opioids are still in the system will precipitate acute, severe withdrawal. This is non negotiable, and it represents the primary clinical challenge in getting patients initiated particularly in settings without supervised detoxification support.

A Cochrane review of 13 randomized trials among 1,158 opioid dependent patients found evidence supporting naltrexone‘s effectiveness when combined with counseling. The injectable formulation has shown particularly strong results in structured settings, including justice involved populations. For more on whole person approaches to men’s mental health and addiction, see our post on Men’s Mental Health.

Naltrexone for Alcohol Use Disorder

Naltrexone‘s evidence base for alcohol use disorder is strong and growing. It works by interfering with the opioid mediated reward response to alcohol reducing the pleasurable sensations that drinking produces and, over time, diminishing cravings.

A meta analysis cited in NCBI StatPearls found that oral naltrexone for preventing heavy drinking showed a number needed to treat (NNT) of 12 meaning one in twelve patients benefits meaningfully from naltrexone who would not benefit from placebo alone. Extended release injectable naltrexone showed even stronger results in that same analysis.

A targeted dosing strategy has also shown promise: patients with mild to moderate AUD who take naltrexone only during periods of high craving or anticipated high risk events have shown meaningful reductions in binge drinking days, total drinks consumed, and alcohol cravings with effects sustained at six months in a published trial. This approach may improve adherence and patient buy in compared to daily dosing.

For patients managing the intersection of alcohol use and mental health challenges like Understanding Burnout or Quiet Burnout in 2026, naltrexone as part of a comprehensive care plan not as a standalone fix represents sound clinical practice.

Naltrexone for Weight Loss: What the Evidence Actually Shows

The weight loss application of naltrexone is one of the most searched topics related to the medication in 2025–2026, and it deserves an honest, evidence grounded treatment.

Naltrexone alone is not FDA approved for weight loss. However, it is a component of Contrave an FDA approved weight management medication combining extended release naltrexone (8 mg) with extended release bupropion (90 mg). In clinical studies of Contrave lasting 52 to 56 weeks, patients achieved significant weight loss compared to placebo with minimal serious side effects.

How does naltrexone contribute to weight loss?

It blocks opioid receptors in the brain’s reward circuit, reducing the dopamine driven pleasure response to palatable, high calorie foods
Research has shown it can make pleasant tastes less rewarding and significantly reduce food intake
One study found that 48 mg of immediate release naltrexone daily produced an average of 1.7% body weight loss over 24 weeks in patients with uncomplicated obesity modest on its own, but more substantial in combination with bupropion
Evidence suggests naltrexone may reduce what researchers call “reward driven eating” eating driven by craving rather than hunger

Naltrexone may be particularly relevant for patients with patterns resembling food addiction or binge eating, because the same opioid reward pathway that drives substance use also plays a role in compulsive overeating. For more clinical context on these overlapping conditions, see our posts on Binge Eating Disorder and Food Addiction.

For the broader weight management context including other medication options see our post on Oral Wegovy vs Injectable: The New Daily Pill for Weight Loss Explained.

Low Dose Naltrexone: An Emerging Off Label Frontier

Beyond its approved uses, naltrexone at very low doses (typically 1.5–4.5 mg, compared to the standard 50 mg) is being studied and used off label for inflammatory and autoimmune conditions including fibromyalgia, Crohn’s disease, multiple sclerosis, and complex regional pain syndrome. The proposed mechanism is different: at low doses, naltrexone may act as an anti inflammatory agent by transiently blocking opioid receptors and triggering an upregulation of the body’s natural endorphin production.

Low dose naltrexone (LDN) is not FDA approved for any of these conditions, and evidence remains preliminary. Patients interested in LDN should have a thorough conversation with their provider about the current evidence, risks, and appropriateness for their specific situation.

Who Should Not Take Naltrexone

Naltrexone is contraindicated or requires careful management in specific populations:

Current opioid users: Taking naltrexone while opioids are present will trigger acute withdrawal. A 7–14 day opioid free period is required before initiation.
Severe liver disease: Naltrexone is metabolized by the liver and has been associated with liver toxicity, particularly at higher doses. Liver function should be assessed before and during treatment.
Patients taking opioid medications for pain: Naltrexone will block the effectiveness of opioid pain medications, making those medications unavailable as pain management tools during treatment.
Pregnancy: Safety during pregnancy has not been established.
Patients under 18: Naltrexone is not recommended for this population.

A critical safety warning that patients and providers must take seriously: when naltrexone is discontinued after a period of use or if a patient relapses their opioid tolerance will be significantly reduced. Returning to prior opioid doses can cause fatal overdose. This information must be clearly communicated to every patient on naltrexone for OUD.

Practical steps to take now:

Ask your provider directly about naltrexone. Many patients who could benefit are never offered it advocacy for yourself or a loved one can change the course of treatment.
Discuss your full medication list. Drug interactions particularly with opioid pain medications require careful review before starting naltrexone.
Reach out to Priority Medical Group. Our whole person care model approaches addiction and weight management together with individualized treatment plans that consider your complete health picture.
Explore telehealth options. Naltrexone for alcohol use disorder can be accessed through telehealth in many states. See our guide on Getting Prescribed Medications Online and Telehealth for Mental Health: What to Expect in 2026.

Don’t wait for crisis. Medication assisted treatment works best when started as part of a proactive, comprehensive care plan not only after rock bottom. Read more at Preventive Mental Health Care: Why Waiting for Crisis Is No Longer the Standard.

FAQ:

1.Is naltrexone addictive?	No naltrexone is not addictive, not an opioid, and produces no intoxicating effects. It cannot be misused to produce euphoria, and it carries no diversion risk. This is one of its key advantages over other medications used in opioid use disorder treatment, such as methadone and buprenorphine, which are themselves controlled substances.
2.How long does it take naltrexone to work?	For alcohol use disorder, patients often notice reduced cravings and diminished pleasure from drinking within the first week. For opioid use disorder, the blocking effect is essentially immediate once the medication is active, opioids cannot produce their effects. Full craving reduction typically develops over weeks of consistent use. The monthly injectable formulation (Vivitrol) reaches therapeutic levels within days of administration.
3.Can naltrexone be used with therapy or counseling?	Absolutely and SAMHSA explicitly describes naltrexone as one component of a comprehensive treatment plan that includes counseling and behavioral health therapies. Research consistently shows that medication assisted treatment is most effective when combined with behavioral support, not used in isolation. Naltrexone addresses the neurobiological dimension; therapy addresses the psychological and social dimensions of addiction.
4.Will naltrexone help me lose weight?	Naltrexone alone produces modest weight loss at standard doses. Its most significant weight management application is as a component of Contrave (naltrexone + bupropion), which is FDA approved for weight management and has demonstrated meaningful weight loss results in 52–56 week clinical trials. Whether naltrexone alone, in Contrave, or in another combination is appropriate for you depends on your individual health profile a conversation your provider is best positioned to have.
5.What are the most common side effects of naltrexone?	The most commonly reported side effects include nausea, headache, fatigue, and decreased appetite. Nausea is most common when starting oral naltrexone and often diminishes over the first two weeks. Taking the medication with food can reduce gastrointestinal symptoms. Serious side effects including liver toxicity are rare but require monitoring, particularly in patients with pre existing liver conditions.
6.Does naltrexone interact with other medications?	Yes most importantly, naltrexone will block all opioid based medications, including prescription pain medications containing opioids. Patients who rely on opioid medications for pain management cannot use naltrexone during those periods without losing pain control. Any patient considering naltrexone should conduct a full medication review with their prescriber to identify and address potential interactions.

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References

SAMHSA. (2024). What Is Naltrexone? Side Effects, Uses, Dose & Risk. https://www.samhsa.gov/substance use/treatment/options/naltrexone
NCBI StatPearls. (2023). Naltrexone. National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK534811/
NCBI Bookshelf. (2021). Chapter 3C: Naltrexone Medications for Opioid Use Disorder. https://www.ncbi.nlm.nih.gov/books/NBK574913/
Drugs.com. (2024). Naltrexone: Uses, Dosage, Side Effects, Warnings. https://www.drugs.com/naltrexone.html
GoodRx. (2025). How Does Naltrexone Work for Opioid and Alcohol Use Disorder? https://www.goodrx.com/naltrexone/naltrexone alcohol drug addiction treatment
SingleCare. (2025). Naltrexone for Weight Loss: Uses, Dosage, and Benefits. https://www.singlecare.com/blog/naltrexone weight loss/
American Journal of Psychiatry. (2023). Naltrexone and Alcohol Use. https://psychiatryonline.org/doi/full/10.1176/appi.ajp.20220821
Hello Klarity. (2025). Naltrexone for Weight Loss: Uses, Effectiveness & More. https://www.helloklarity.com/post/naltrexone weight loss/
U.S. Food and Drug Administration. (2024). Vivitrol (naltrexone for extended release injectable suspension) Prescribing Information. https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=021897
World Health Organization. (2024). Alcohol. https://www.who.int/news room/fact sheets/detail/alcohol

Disclaimer

This article is for educational and informational purposes only and does not constitute medical, legal, or financial advice. Reading this content does not establish a patient provider relationship with Priority Medical Group or any of its clinicians. Naltrexone is a prescription medication that must be initiated and monitored by a licensed healthcare provider. If you or someone you know is struggling with substance use, call SAMHSA’s National Helpline at 1 800 662 4357 (free, confidential, 24/7) or text 988 (Suicide & Crisis Lifeline) if in crisis.

For questions about Priority Medical Group services, visit pmgcare.com

Understanding Naltrexone: How It Works for Addiction and Weight Loss