Naltrexone

Indications

Naltrexone is used for: Opioid dependence, Alcohol dependence

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

Child Dose

Safety and efficacy not established

Renal Dose

Administration

May be taken with or without food.

Contra Indications

Patients concurrently dependent on opioids; acute hepatitis or hepatic failure; acute opioid withdrawal; patients on therapeutic opioid analgesics.

Precautions

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).

Pregnancy-Lactation

Pregnancy The available data from published case series with use in pregnant women are insufficient to identify a drug-associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes Untreated opioid addiction in pregnancy is associated with adverse obstetrical outcomes such as low birth weight, preterm birth, and fetal death; in addition, untreated opioid addiction often results in continued or relapsing illicit opioid use Published studies have demonstrated that alcohol is associated with fetal harm including growth restriction, facial abnormalities, central nervous system abnormalities, behavioral disorders, and impaired intellectual development Lactation The drug and metabolites, are present in human milk; there are no data on effects on breastfed infant or on milk production Developmental health benefits of breastfeeding should be considered along with mother’s clinical need for naltrexone and any potential adverse effects on breastfed infant from drug or mother’s underlying maternal condition

Interactions

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.

Adverse Effects

Side effects of Naltrexone : >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

Mechanism of Action

Naltrexone acts as a competitive antagonist at opioid receptor sites. It blocks the action of opioids and precipitates withdrawal symptoms in opioid-dependent individuals.