Approved indications: Oral naltrexone is approved in adults for treatment of alcohol use disorder (to help reduce heavy drinking and support abstinence) and for prevention of relapse in opioid-dependent patients who have been detoxified and are opioid-free for an adequate period.

Off-label uses and evidence: Clinicians sometimes use oral or low-dose naltrexone off-label for conditions such as chronic pain syndromes (e.g., fibromyalgia), certain autoimmune or inflammatory diseases, impulse-control or eating disorders, and weight management, but evidence is limited to small or mixed-quality studies and these uses are not FDA-approved.

Efficacy expectations in alcohol use disorder: Many people notice reduced craving or fewer heavy-drinking episodes within the first 1–2 weeks, with typical benefits including more alcohol-free days and fewer relapses when combined with counseling; it usually does not make people abstinent on its own and works best as part of a structured program.

Efficacy expectations in opioid use disorder: When started after complete opioid detoxification and taken consistently, naltrexone effectively blocks opioid effects and reduces relapse risk, but real-world success is limited by adherence, so it is often reserved for highly motivated patients or those with supervised dosing.

Comparison to similar drugs: Unlike methadone or buprenorphine, naltrexone is a pure antagonist with no abuse potential or physical dependence, but its overall effectiveness can be lower because missing doses quickly removes protection; compared with other alcohol-use-disorder medicines (such as acamprosate or disulfiram), its benefit is moderate and selection depends on patient goals, liver function, and comorbidities.

Typical adult dosing (oral tablets): For alcohol use disorder, a common regimen is 50 mg by mouth once daily; for opioid use disorder, clinicians often begin with a 25 mg test dose (to check for withdrawal or intolerance) and then increase to 50 mg once daily, with some supervised programs using alternative schedules such as 100 mg on certain days.

How to take: Swallow tablets whole with water, with or without food (taking with food may lessen nausea), at roughly the same time each day; do not start naltrexone until you have been opioid-free for the recommended interval (often 7–10 days for short-acting opioids, longer for long-acting agents) as directed by your clinician.

Special dosing instructions: Dose reductions or slower titration may be used in older adults or those with mild to moderate liver or kidney problems, and treatment is usually combined with counseling and behavioral therapies; do not take any opioid medicines, including some cough, cold, or anti-diarrheal products, while on naltrexone unless specifically managed by a specialist.

Missed dose guidance: If you miss a dose, take it as soon as you remember on the same day, but if it is almost time for the next scheduled dose, skip the missed dose and resume your regular schedule—do not double up to make up for a missed tablet.

Overdose management: Taking more than prescribed can increase side effects, particularly liver toxicity; there is no specific antidote, so in case of suspected overdose or severe symptoms (such as intense nausea, vomiting, abdominal pain, confusion, or collapse), seek emergency medical care and contact a poison control center immediately.

Common side effects: Frequently reported effects include nausea, stomach pain, loss of appetite, vomiting, headache, dizziness, fatigue, anxiety, sleep problems, and joint or muscle aches; these are usually mild to moderate and often improve over days to weeks, especially if treatment is started at a lower dose or taken with food.

Serious or rare adverse effects: Naltrexone can cause liver injury, particularly at higher-than-recommended doses or in people with pre-existing liver disease, so new or worsening fatigue, dark urine, pale stools, abdominal pain, or yellowing of the skin or eyes require urgent medical evaluation; sudden opioid withdrawal can occur if it is started while opioids are still in the body, and attempts to “override” the blockade with large opioid doses can lead to life-threatening overdose.

Warnings and precautions: It is contraindicated in people who are currently physically dependent on opioids, with a positive opioid screen, in acute hepatitis, or in liver failure; use with caution and close monitoring in chronic liver disease or severe kidney impairment, and it is not approved for children or adolescents under 18 years, while in pregnancy or breastfeeding it is generally reserved for situations where potential benefits clearly outweigh uncertain risks.

Relative safety compared with other options: Naltrexone is not habit-forming and does not cause sedation or respiratory depression like opioid agonists, but it carries more concern for liver toxicity than some alternatives and removes the analgesic effect of opioid pain medicines, which must be considered if serious pain or surgery is anticipated.

Reporting and safety updates: Patients and caregivers can report suspected side effects to the FDA MedWatch program or to their healthcare professional or pharmacist, and up-to-date safety information can be found on official FDA and medication-guide resources for naltrexone.

Opioid-related interactions: Naltrexone blocks the effects of all opioid medicines, including prescription pain relievers (such as oxycodone, hydrocodone, morphine, fentanyl), opioid dependence treatments (methadone, buprenorphine), and many cough or cold preparations containing codeine or hydrocodone; using these together can cause sudden withdrawal in dependent individuals or loss of pain control.

Other drugs, supplements, and alcohol: Because naltrexone is processed by the liver, combining it with other medicines that can stress the liver (for example high-dose acetaminophen, some tuberculosis or seizure drugs, or heavy ongoing alcohol use) may raise the risk of liver problems, so your clinician will review all prescription and nonprescription medicines, herbal products, and supplements you take.

Precautions and contraindications: Naltrexone should not be used in people with acute hepatitis, liver failure, or current physiological opioid dependence, and it is used cautiously in those with chronic liver disease, severe kidney impairment, a history of severe depression or suicidal thoughts, or in pregnant or breastfeeding individuals.

Monitoring needs: Before and during therapy, clinicians typically assess for recent opioid use (often with history and urine testing) and check baseline and periodic liver function tests; they may also monitor mood, suicidality, and adherence, and may plan ahead for situations where opioid pain medication could be needed, such as emergency care or surgery.

Procedures and imaging: Naltrexone does not usually interfere with imaging contrast agents or most diagnostic tests, but because it blocks opioid pain medicines, patients should inform all healthcare providers (including dentists and emergency staff) that they are taking naltrexone before any procedure where pain control might be required.

Q: Can I drink alcohol while taking naltrexone?
A: Naltrexone is prescribed to help you reduce or stop drinking, so you are usually advised to avoid alcohol; if you do drink, the medication may reduce the pleasure you feel but drinking can still harm your liver and may undermine your treatment goals.

Q: How long does it take for naltrexone to start working?
A: Naltrexone begins blocking opioid receptors within hours of the first dose, and many people notice reduced cravings or fewer heavy-drinking episodes within the first 1–2 weeks, especially when combined with counseling and support.

Q: Will I have withdrawal symptoms if I stop naltrexone?
A: Naltrexone is not an opioid and does not cause physical dependence, so stopping it does not produce classic withdrawal, but your cravings or risk of relapse can increase once the medication is out of your system.

Q: What if I need surgery or strong pain medicine while on naltrexone?
A: Because naltrexone blocks opioid pain relievers, you should tell all your healthcare providers that you take it; for planned procedures your prescriber may advise stopping it ahead of time, and in emergencies doctors may use non-opioid pain strategies or higher-level monitored care if opioids are required.

Q: Does naltrexone cause weight loss?
A: Naltrexone alone is not approved or usually prescribed specifically for weight loss, although a separate combination product containing naltrexone and bupropion is approved for chronic weight management in certain adults, and any weight change with naltrexone alone is typically modest and variable.

Storage: Store tablets at room temperature (about 68–77°F / 20–25°C), in the original tightly closed, light-resistant container, away from moisture, heat, and direct light, and out of reach of children and pets.

Disposal: When no longer needed, use a pharmacy or community drug take-back program if available; if none is available, mix tablets (do not crush) with an unappealing substance (such as used coffee grounds or cat litter), seal in a bag or container, and place in the household trash, and do not flush the medication down the toilet unless specifically instructed.