Trade Names:ReVia- Tablets 50 mg
Trade Names:Vivitrol- Suspension, extended-release injection 380 mg per vial
Opioid receptor antagonist markedly attenuating or completely blocking, reversibly, the subjective effects of IV administered opioids.
Rapidly and nearly completely absorbed (96%) from the GI tract.Extended-release injectable suspension
Transient initial peak within 2 h, followed by a second peak approximately 2 to 3 days later. About 14 days after dosing, concentrations decline slowly, with measurable levels for more than 1 mo. Exposure is 3- to 4-fold higher following IM administration compared with oral naltrexone.
Vd is estimated to be 1,350 L. Plasma protein binding is 21%.
Over 98% metabolized and extrahepatic sites may exist. The major metabolite is 6-β-naltrexol, which accounts for 43% of an oral dose. There are 2 minor metabolites. Less 6-β-naltrexone is generated after IM administration compared with oral.
Renal Cl of naltrexone ranges from 30 to 127 mL/min, suggesting that renal elimination is primarily glomerular filtration. Urinary excretion of unchanged naltrexone is less than 2%, while urinary excretion of unchanged and conjugated 6-β-naltrexol accounts for 43%. Naltrexone and its metabolites may undergo enterohepatic recirculation.
Following administration of the extended-release injectable suspension, the elimination t ½ is 5 to 10 days.
Alcohol dependence; blockade of exogenously administered opioids (oral); treatment of alcohol dependence in patients able to abstain from alcohol in an outpatient setting (IM injection).
Eating disorders; postconcussional syndrome unresponsive to other treatments.
Receiving opioid analgesics; currently dependent on opioids, including those maintained on opiate agonists (eg, methadone); in acute opioid withdrawal; patients who have failed the naloxone challenge test or have positive urine screen for opioids; a history or sensitivity to naloxone or the phenanthrene-containing opioids; acute hepatitis or liver failure (oral).
PO 50 mg once daily for up to 12 wk is sufficient for most patients. IM 380 mg every 4 wk or once a month.Opioid DependenceAdults
PO Start with 25 mg; if no withdrawal signs occur, patient may be started on 50 mg daily thereafter. Do not attempt treatment if patient has not remained opioid-free for at least 7 to 10 days or if signs of opioid withdrawal are observed following naloxone challenge.
Store tablets at controlled room temperature (59° to 86°F). Store entire dose pack of the injectable suspension in the refrigerator (36° to 46°F). Store unrefrigerated at temperatures not exceeding 77°F for no more than 7 days. Do not freeze.
May increase the risk of hepatotoxicity.Opioid-containing medication
Because of antagonistic effects of naltrexone, patients may not benefit from opioid medication.Thioridazine
Lethargy and somnolence have been reported with coadministration of naltrexone.
None well documented.
Headache (36%); dizziness/syncope (16%); depression (0% to 15%); insomnia, sleep disorder (14%); low energy, nervousness (more than 10%); feeling down, increased energy, irritability, loss of appetite (less than 10%); fatigue (4%); anxiety, sedation/somnolence (2%); suicidal attempt/ideation (1% or less).
Skin rash (12%).
Nausea (33%); dry mouth (24%); abdominal pain (16%); vomiting (14%); diarrhea (13%); abdominal cramps (more than 10%); increased thirst (less than 10%); constipation (3%).
Decreased potency, delayed ejaculation (less than 10%).
Increased AST (2%); decreased platelet count, increased CPK, increased eosinophil count.
Tenderness (72%); induration (35%); other injection-site reactions, including nodules and swelling (32%); asthenic conditions (23%); pain (17%); pruritus (10%); ecchymosis (7%).
Anorexia/appetite decreased/appetite disorder (20%).
Arthralgia/arthritis/joint stiffness (12%); joint and muscle pain (more than 10%); muscle cramps (8%); back pain/stiffness (7%).
Upper respiratory tract infection (13%).
Naltrexone has the capacity to cause hepatocellular injury when given in excessive doses.
Assess liver function (eg, alkaline phosphatase, bilirubin, transaminases) before starting therapy, and periodically thereafter based on clinical situation and dose of naltrexone.
Category C .
Safety and efficacy not established.
Because naltrexone and its primary metabolite are excreted mainly in the urine, use with caution in patients with moderate to severe renal function impairment.
Use with caution in patients with renal or hepatic function impairment.
To prevent occurrence of an acute abstinence syndrome, patient must be opioid-free for a minimum of 7 to 10 days.
Severe opioid withdrawal syndromes precipitated by accidental ingestion of naltrexone may occur in opioid-dependent individuals. Withdrawal symptoms may appear within 5 min and last 48 h.
Do not perform in patients showing clinical signs or symptoms of opioid withdrawal or in patients whose urine contains opioids.
Overcoming the antagonism by taking opioids is dangerous and may lead to fatal overdose.
Safe use has not been established.
Risk is not abated by naltrexone treatment.
Abdominal pain, dizziness, nausea, somnolence.
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