Adult Dose
Opioid Dependence
Prevention of relapse after opioid detoxification; to be used only after patient has been opioid-free for 7-10 days and after negative naloxone challenge (no symptom withdrawal after naloxone administration)
PO: 25 mg initially, then observation for 1 hr, then 50 mg once daily starting on day 2; flexible dosing regimens can be employed to accommodate patient convenience or ensure compliance
IM: 380 mg in gluteal muscle every 4 weeks for maintenance of abstinence
Alcohol Dependence
Treatment in patients who have been able to abstain from alcohol in outpatient settings before treatment initiation
PO: 50 mg once daily for <12 weeks
IM: 380 mg in gluteal muscle every 4 weeks for maintenance of abstinence
Precaution
Hepatic or renal impairment. Monitor LFTs regularly. Patients should be opioid-free for at least 7-10 days prior to initiating naltrexone therapy. Strictly warn patients against the use of opioids while on naltrexone. Monitor for inj-site reactions. Pregnancy, lactation. History of bleeding disorders (including thrombocytopenia).
Side Effect
>10%
Injection site reaction (69%; includes bruising, induration, nodules, pain, pruritus, swelling, tenderness)
Nausea (33%),Headache (25%),Decreased appetite (14%),Insomnia (14%),Vomiting (14%),Diarrhea (13%),Dizziness (13%),Upper respiratory tract infection (URTI) (13%),Anxiety (12%),Arthralgia (12%),Increased creatine phosphokinase (11%),Pharyngitis (11%)
1-10%
Depression (8%),Muscle cramps (8%),Back pain (6%),Rash (6%),Dry mouth (5%),Somnolence (4%),Increased aspartate aminotransferase (AST) (2%)
<1%
Alopecia,Dyspnea,Edema,Hepatocellular injury,Increased systolic and diastolic blood pressures,Liver function abnormalities,Labored breathing,Nonspecific electrocardiographic (ECG) changes,Opiate withdrawal (mild to severe signs and symptoms, including drug craving, confusion, drowsiness, visual hallucinations, abdominal pain, vomiting, diarrhea),Palpitation,Phlebitis,Tachycardia
Interaction
May reduce effects of opiate-containing preparations e.g. those used for cough and cold, diarrhoea and pain. Increased or decreased serum levels with drugs that alter hepatic metabolism. Potentially increased hepatotoxic effects with disulfiram. Increased risk of naltrexone-induced lethargy and somnolence with thioridazine. May increase insulin requirements.