Overview
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.
Mechanism of Action
CLINICAL PHARMACOLOGY Pharmacodynamic Actions Naltrexone hydrochloride is a pure opioid antagonist. It markedly attenuates or completely blocks, reversibly, the subjective effects of intravenously administered opioids. When coadministered with morphine, on a chronic basis, naltrexone hydrochloride blocks the physical dependence to morphine, heroin and other opioids. Naltrexone hydrochloride has few, if any, intrinsic actions besides its opioid blocking properties. However, it does produce some pupillary constriction, by an unknown mechanism. The administration of naltrexone hydrochloride is not associated with the development of tolerance or dependence. In subjects physically dependent on opioids, naltrexone hydrochloride will precipitate withdrawal symptomatology.
Indications
- 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.
Common Doses
- 50 mg
- 25 mg
- 0.2 mg
- 0.6 mg
Dosage
DOSAGE AND ADMINISTRATION To reduce the risk of precipitated withdrawal in patients dependent on opioids, or exacerbation of a preexisting subclinical withdrawal syndrome, opioid-dependent patients, including those being treated for alcohol dependence, should be opioid-free (including tramadol) before starting naltrexone hydrochloride treatment. An opioid-free interval of a minimum of 7 to 10 days is recommended for patients previously dependent on short-acting opioids.
Contraindications
- 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.
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.
Interactions
- 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.