Comparative Pharmacology
Head-to-head clinical analysis: NARCAN versus VIVITROL.
Peer-Reviewed Evidence
Head-to-head clinical analysis: NARCAN versus VIVITROL.
NARCAN vs VIVITROL
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Opioid receptor antagonist; binds competitively to mu, kappa, and delta opioid receptors, reversing opioid effects.
Naltrexone, as the active moiety of VIVITROL, is a competitive antagonist at opioid receptors (mu, kappa, and delta), blocking the euphoric effects of alcohol and opioids. It also modulates the hypothalamic-pituitary-adrenal axis and dopamine pathways implicated in alcohol craving.
Initial dose: 0.4 mg to 2 mg IV, IM, or SC, repeated every 2 to 3 minutes as needed. For opioid-induced respiratory depression, may use 0.1 to 0.2 mg IV increments in patients with opioid dependence to avoid withdrawal.
380 mg intramuscularly every 4 weeks, alternating gluteal injections.
None Documented
None Documented
Approximately 1 hour in adults; context: shorter than most opioids (e.g., morphine 2-4 h), necessitating repeated doses for prolonged opioid effects.
Naltrexone terminal half-life: 4-13 hours (mean 9.7 h). Active metabolite 6-β-naltrexol: 10-15 hours. Clinically, naltrexone concentrations are sustained for ~30 days after IM injection.
Primarily hepatic metabolism (glucuronidation) followed by renal excretion of metabolites; <5% excreted unchanged in urine.
Naltrexol (6-β-naltrexol) and naltrexone: primarily renal (60-70% as metabolites, <5% as unchanged drug); biliary/fecal (minor route, <10%).
Category C
Category C
Opioid Antagonist
Opioid Antagonist