• Alcohol dependence: To help maintain abstinence.
  • Opioid dependence: As part of a comprehensive treatment program after detoxification.

Dosage:

  • Alcohol dependence: 50 mg orally once daily.
  • Opioid dependence:
  • Initiate at least 7–10 days after last opioid use to avoid precipitated withdrawal.
  • Oral: 25 mg test dose, then 50 mg daily if no withdrawal.
  • Injectable (extended-release): 380 mg IM every 4 weeks or once a month (gluteal muscle).
  • OP: 50 mg
  • IM: 380 mg/vial 
  • Must be opioid-free for at least 7–10 days before starting.
  • Can be taken with or without food.
  • Regular follow-up and counseling are recommended as part of treatment.

Mechanism of Action:

  • Naltrexone is a pure opioid antagonist.
  • It blocks mu-opioid receptors, reducing the euphoric effects of opioids and alcohol.
  • Helps reduce craving and relapse risk.

Pharmacokinetics:

  • Oral bioavailability: ~5–40%
  • Onset: 15–30 minutes (oral)
  • Half-life: ~4 hours (naltrexone), 13 hours (active metabolite: 6-β-naltrexol)
  • Metabolism: Hepatic
  • Excretion: Renal

Common:

  • Nausea
  • Headache
  • Dizziness
  • Fatigue
  • Insomnia
  • Anxiety

Serious:

  • Hepatotoxicity (dose-related)
  • Depression, suicidal thoughts
  • Injection site reactions (for IM form)
  • Precipitated opioid withdrawal (if opioids are still in system)
  • Current opioid use or opioid dependence
  • Acute opioid withdrawal
  • Hepatic failure
  • Hypersensitivity to naltrexone or formulation components
  • Opioid analgesics: Reduced or blocked effect of opioids (analgesia may be ineffective)
  • May reduce the efficacy of opioid-containing cough and cold medications.
  • No significant CYP450 interactions.

                                   Drug Status

Availability
Pregnancy
Breastfeeding
Schedule
BRAND NAME STRENGTH FORMULATION PACK SIZE MANUFACTURER DISTRIBUTOR
Addtrex 765mg Implant 1’s Rusan Pharma Surgilinks Ltd