Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
Quick facts
- How it is given
- oral
- Type
- human prescription drug
- RxNorm ID
- 1483744
We do not publish dosing. How much of this medicine to take, how often, and for how long depends on your age, weight, kidney and liver function, other conditions and other medicines. That is a decision for the person who prescribes or dispenses it. Follow the directions on your own pack and ask your pharmacist if anything is unclear.
What it is used to treat
INDICATIONS AND USAGE Naltrexone hydrochloride tablets USP 50 mg is indicated in the treatment of alcohol dependence and for the blockade of the effects of exogenously administered opioids. Naltrexone hydrochloride tablets USP 50 mg has not been shown to provide any therapeutic benefit except as part of an appropriate plan of management for the addictions.
About this medicine
DESCRIPTION Naltrexone hydrochloride, an opioid antagonist, is a synthetic congener of oxymorphone with no opioid agonist properties. Naltrexone differs in structure from oxymorphone in that the methyl group on the nitrogen atom is replaced by a cyclopropylmethyl group. Naltrexone hydrochloride is also related to the potent opioid antagonist, naloxone, or n-allylnoroxymorphone. The chemical name for naltrexone hydrochloride is Morphinan-6-one, 17-(cyclopropylmethyl)-4,5-epoxy-3,14-dihydroxy-, hydrochloride, (5α)-. The structural formula is as follows: Naltrexone hydrochloride is a white, crystalline compound. The hydrochloride salt is soluble in water to the extent of about 100 mg/mL. Naltrexone hydrochloride tablets,50 mg is available in film coated tablets, containing 50 mg of naltrexone hydrochloride USP. Naltrexone hydrochloride tablets 50 mg also contain: colloidal anhydrous silica, crospovidone, hydroxypropyl methylcellulose, lactose monohydrate, magnesium stearate, microcrystalline cellulose, polyethylene glycol 400, polysorbate 80, iron oxide red, iron oxide yellow and titanium dioxide. Chemical Structure
Who should not take it
CONTRAINDICATIONS Naltrexone hydrochloride is contraindicated in Patients receiving opioid analgesics. Patients currently dependent on opioids, including those currently maintained on opiate agonists (e.g., methadone ) or partial agonists (e.g., buprenorphine) Patients in acute opioid withdrawal (see WARNINGS ). Any individual who has failed the naloxone challenge test or who has a positive urine screen for opioids. Any individual with a history of sensitivity to naltrexone hydrochloride or any other components of this product.It is not known if there is any cross-sensitivity with naloxone or the phenanthrene containing opioids.
Warnings
WARNINGS Vulnerability to Opioid Overdose After opioid detoxification, patients are likely to have reduced tolerance to opioids. As the blockade of exogenous opioids provided by naltrexone hydrochloride wanes and eventually dissipates completely, patients who have been treated with naltrexone hydrochloride may respond to lower doses of opioids than previously used, just as they would shortly after completing detoxification. This could result in potentially life-threatening opioid intoxication (respiratory compromise or arrest, circulatory collapse, etc.) if the patient uses previously tolerated doses of opioids. Cases of opioid overdose with fatal outcomes have been reported in patients after discontinuing treatment. Patients should be alerted that they may be more sensitive to opioids, even at lower doses, after naltrexone hydrochloride treatment is discontinued. It is important that patients inform family members, and the people closest to the patient of this increased sensitivity to opioids and the risk of overdose. (see PRECAUTIONS, Information for Patients ). There is also the possibility that a patient who is treated with naltrexone hydrochloride could overcome the opioid blockade effect of naltrexone hydrochloride. Although naltrexone hydrochloride is a potent antagonist , the blockade produced by naltrexone hydrochloride is surmountable. The plasma concentration of exogenous opioids attained immediately following their acute administration may be sufficient to overcome the competitive receptor blockade. This poses a potential risk to individuals who attempt, on their own, to overcome the blockade by administering large amounts of exogenous opioids.Any attempt by a patient to overcome the antagonism by taking opioids is especially dangerous and may lead to life-threatening opioid intoxication or fatal overdose. Patients should be told of the serious consequences of trying to overcome the opioid blockade (see PRECAUTIONS, Information for Patients ). […]
Reported side effects
ADVERSE REACTIONS During two randomized, double-blind placebo-controlled 12 week trials to evaluate the efficacy of naltrexone hydrochloride as an adjunctive treatment of alcohol dependence, most patients tolerated naltrexone hydrochloride well. In these studies, a total of 93 patients received naltrexone hydrochloride at a dose of 50 mg once daily. Five of these patients discontinued naltrexone hydrochloride because of nausea. No serious adverse events were reported during these two trials. While extensive clinical studies evaluating the use of naltrexone hydrochloride in detoxified, formerly opioid-dependent individuals failed to identify any single, serious untoward risk of naltrexone hydrochloride use, placebo-controlled studies employing up to five-fold higher doses of naltrexone hydrochloride (up to 300 mg per day) than that recommended for use in opiate receptor blockade have shown that naltrexone hydrochloride causes hepatocellular injury in a substantial proportion of patients exposed at higher doses (see WARNINGS and PRECAUTIONS: Laboratory Tests ). Aside from this finding, and the risk of precipitated opioid withdrawal, available evidence does not incriminate naltrexone hydrochloride, used at any dose, as a cause of any other serious adverse reaction for the patient who is“opioid free.” It is critical to recognize that naltrexone hydrochloride can precipitate or exacerbate abstinence signs and symptoms in any individual who is not completely free of exogenous opioids. Patients with addictive disorders, especially opioid addiction, are at risk for multiple numerous adverse events and abnormal laboratory findings, including liver function abnormalities. Data from both controlled and observational studies suggest that these abnormalities, other than the dose-related hepatotoxicity described above, are not related to the use of naltrexone hydrochloride. Among opioid free individuals, naltrexone hydrochloride administration at the recommended dose has not been associated with a predictable profile of serious adverse or untoward events. […]
Interactions with other medicines
Drug Interactions Studies to evaluate possible interactions between naltrexone hydrochloride and drugs other than opiates have not been performed. Consequently, caution is advised if the concomitant administration of naltrexone hydrochloride and other drugs is required. The safety and efficacy of concomitant use of naltrexone hydrochloride and disulfiram is unknown, and the concomitant use of two potentially hepatotoxic medications is not ordinarily recommended unless the probable benefits outweigh the known risks. Lethargy and somnolence have been reported following doses of naltrexone hydrochloride and thioridazine. Patients taking naltrexone hydrochloride may not benefit from opioid containing medicines, such as cough and cold preparations, antidiarrheal preparations, and opioid analgesics. In an emergency situation when opioid analgesia must be administered to a patient receiving naltrexone hydrochloride, the amount of opioid required may be greater than usual, and the resulting respiratory depression may be deeper and more prolonged (see PRECAUTIONS )
If too much is taken
OVERDOSAGE There is limited clinical experience with naltrexone hydrochloride overdosage in humans. In one study, subjects who received 800 mg daily naltrexone hydrochloride for up to one week showed no evidence of toxicity. In the mouse, rat and guinea pig, the oral LD 50s were 1,100 to 1,550 mg/kg; 1,450 mg/kg; and 1,490 mg/kg; respectively. High doses of naltrexone hydrochloride (generally ≥ 1,000 mg/kg) produced salivation, depression/reduced activity, tremors, and convulsions. Mortalities in animals due to high-dose naltrexone hydrochloride administration usually were due to clonic-tonic convulsions and/or respiratory failure. Treatment of Overdosage In view of the lack of actual experience in the treatment of naltrexone hydrochloride overdose, patients should be treated symptomatically in a closely supervised environment. Physicians should contact a poison control center for the most up-to-date information.
Before you take anything new
Tell your pharmacist or doctor about every medicine you take — including ones bought without a prescription, herbal products and supplements. Interactions are one of the most common avoidable causes of harm from medicines, and a pharmacist can check your full list in a couple of minutes.
This page is built from the openFDA record of the U.S. Food and Drug Administration's approved labelling for this product, effective 15 December 2023. Label text has been shortened and reformatted for readability; safety wording has not been altered in meaning. FDA labelling describes products approved in the United States — brand names, strengths, formulations and approved uses may differ in your country. Always read the leaflet that comes with your own pack. PocketsInfo is not affiliated with, and is not endorsed by, the FDA. Retrieved 2026-07-30.