(naltrexone) for Extended-Release Injectable Suspension Intramuscular
Naltrexone has the capacity to cause hepatocellular injury when given in excessive doses.
Naltrexone is contraindicated in acute hepatitis or liver failure, and its use in patients with active liver disease must be carefully considered in light of its hepatotoxic effects.
The margin of separation between the apparently safe dose of naltrexone and the dose causing hepatic injury appears to be only five-fold or less. VIVITROL (naltrexone xr inj) does not appear to be a hepatotoxin at the recommended doses.
Patients should be warned of the risk of hepatic injury and advised to seek medical attention if they experience symptoms of acute hepatitis. Use of VIVITROL (naltrexone xr inj) should be discontinued in the event of symptoms and/or signs of acute hepatitis [see WARNINGS AND PRECAUTIONS]
VIVITROL® (naltrexone for extended-release injectable suspension) is supplied as a microsphere formulation of naltrexone for suspension, to be administered by intramuscular injection. Naltrexone is an opioid antagonist with little, if any, opioid agonist activity.
Naltrexone is designated chemically as morphinan-6-one, 17 (cyclopropylmethyl) 4,5-epoxy-3,14-dihydroxy-(5α) (CAS Registry # 16590-41-3). The molecular formula is C20H23NO4 and its molecular weight is 341.41 in the anhydrous form (i.e., < 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 168-170° C (334-338° F). It is insoluble in water and is soluble in ethanol.
VIVITROL (naltrexone xr inj) is provided as a carton containing a vial each of VIVITROL (naltrexone xr inj) microspheres and diluent, one 5-mL syringe, one 1-inch 20-gauge preparation needle, two 1.5-inch 20-gauge and two 2-inch 20-gauge administration needles with needle protection device.
VIVITROL (naltrexone xr inj) microspheres consist of a sterile, off-white to light tan powder that is available in a dosage strength of 380 mg naltrexone per vial. 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 a clear, colorless solution. The composition of the diluent includes carboxymethylcellulose sodium salt, polysorbate 20, sodium chloride, and water for injection. The microspheres must be suspended in the diluent prior to injection.
What are the possible side effects of naltrexone injection (Vivitrol)?
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have any of these serious side effects:
- blurred vision or eye problems;
- fast heartbeat;
- wheezing, difficulty breathing;
- mood changes, hallucinations (seeing or hearing things), confusion, thoughts of hurting yourself;
- nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or...
What are the precautions when taking naltrexone xr inj (Vivitrol)?
Before using naltrexone, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you: have taken any type of opioid drugs (e.g., codeine, oxycodone, morphine) in the last 7 to 10 days, are currently withdrawing from or dependent on any opioid (including methadone maintenance), currently have liver disease/liver failure.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: bleeding problems (e.g., hemophilia, low...
Last reviewed on RxList: 11/8/2010
This monograph has been modified to include the generic and brand name in many instances.
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