naltrexone - Generic Medications

VIVITROL ® (naltrexone for extended-release injectable suspension) is supplied as a microsphere formulation of naltrexone for suspension, to be administered by deep intramuscular injection by a healthcare practitioner. VIVITROL contains naltrexone base anhydrous as the active pharmaceutical ingredient. Naltrexone is an opioid antagonist with little, if any, opioid agonist activity. Naltrexone is morphinan-6-one, 17-(cyclopropylmethyl)-4,5-epoxy-3,14-dihydroxy-(5α) (CAS Registry # 16590-41-3). The molecular formula is C 20 H 23 NO 4 and its molecular weight is 341.41 in the anhydrous form (ie, < 1% maximum water content). The structural formula is: Naltrexone base anhydrous is an off-white to a light tan powder with a melting point of 168 °C to 170 °C (334 °F to 338 °F). It is insoluble in water and is soluble in ethanol. VIVITROL is provided in a carton containing one vial of VIVITROL microspheres, one vial of diluent, one 5-mL syringe, one 1-inch 20-gauge preparation needle, two 1 1/2-inch 20-gauge, and two 2-inch 20-gauge administration needles with needle protection device. VIVITROL microspheres consist of a sterile, off-white to light tan powder that is available in a dosage strength of 380 mg of naltrexone per vial. Naltrexone base anhydrous is incorporated in a biodegradable matrix of 75:25 polylactide-co-glycolide (PLG) at a concentration of 337 mg of naltrexone per gram of microspheres. The diluent is a clear, colorless solution. Each mL of diluent contains 30.0 mg of carboxymethylcellulose sodium, 1.0 mg of polysorbate 20, 9.0 mg of sodium chloride, and sodium hydroxide and hydrochloric acid as pH adjusters, in water for injection. The pH of the diluent is in the range of 5.8 to 7.2. Naltrexone Structural Formula