Low Dose Naltrexone

Like naloxone, naltrexone is a competitive antagonist at opiate receptors mu, kappa, and delta. Opiate receptors have been reclassified by an International Union of Pharmacology subcommittee as OP1 (delta), OP2 (kappa), and OP3 (mu). Naltrexone can either displace opiate agonists from binding at these receptors or prevent opiate binding. Naltrexone does not antagonize the effects of non-opiates such as cocaine, ethanol, amphetamines, barbiturates, or benzodiazepines. Blockade of opiate receptors by naltrexone is a competitive phenomenon and results in elimination of the euphoric effect of opiates. At usual opiate concentrations, naltrexone’s greater affinity for the receptor prevents the binding of the opiate agonist to the receptor. However, when opiate concentrations are extremely high, the opiate can displace naltrexone, and respiratory depression and/or death is possible. Although naltrexone itself may possess some agonistic properties, these are minor compared to its potent antagonistic actions. Naltrexone is 17-times more potent than nalmorphine and twice as potent as naloxone. In patients who are physically dependent on opiates, naltrexone will precipitate an opiate withdrawal syndrome. Naltrexone use is not associated with tolerance or dependence, therefore, withdrawal from naltrexone does not occur. When co-administered with opiate agonists, naltrexone blocks the physical dependence to morphine, heroin, and other opiate agonists. Depending on the dose, the clinical effects of naltrexone can persist for up to 72 hours.

Naltrexone is contraindicated in patients with hypersensitivity to naltrexone or any components of the commercially available product. Naltrexone is incorporated in 75:25 polylactide-co-glycolide (PLG) at a concentration of 337 mg of naltrexone per gram of microspheres. The diluent is composed of carboxymethylcellulose sodium salt, polysorbate 20, sodium chloride, and water for injection. Naltrexone should also not be used in patients with a known hypersensitivity to naloxone or nalmefene because these three drugs are all structurally similar.

Please discuss with your healthcare provider.

Please discuss with your healthcare provider.

Store this medication at 68°F to 77°F (20°C to 25°C) and away from heat, moisture and light. Keep all medicine out of the reach of children. Throw away any unused medicine after the beyond use date. Do not flush unused medications or pour down a sink or drain.