Naltrexone

Aka: Naltrexone, Trexan, Revia, Vivitrol

1. Indications
   1. Substance Dependence (especially with history of relapse)
      1. Alcoholism
      2. Opioid Dependence
      3. Must be used with an aftercare program
   2. Low dose Naltrexone (0.5 mg to 4.5 mg/day) has also been proprosed for various conditions including Chronic Pain
      1. No rigorous evidence of benefit at these low doses and for these varied conditions, but unlikely to cause harm
      2. Postulated to up-regulate Opioid receptors, increas endorphin production and act as Analgesic and antiinflammatory
      3. May cause Opioid Withdrawal if used soon after last use of Opioids
      4. (2020) Presc Lett 27(4): 22
      5. Toljan (2018) Med Sci 6(4): 82 [PubMed]
2. Contraindications
   1. Long-term Opioid use or Heroin dependence (until off Opioids for at least 7-10 days)
      1. Risk of severe withdrawal
   2. Opioids needed for pain control
   3. Hepatitis or Liver failure
3. Adverse effects
   1. Hepatotoxicity (dose dependent)
   2. Nausea (10%)
   3. Headache
   4. Anxiety
   5. Sedation
4. Mechanism
   1. Reduces Alcohol craving
   2. Decreases impulsive use of Opioids
5. Efficacy
   1. Initial studies showed relapse reduction by 50%
   2. Recent large DBPCT showed no benefit with Naltrexone
      1. Relapse rate: 38% at 13 weeks (44% with Placebo)
      2. Compliance rate low: 42-44% in all groups
      3. Krystal (2001) N Engl J Med 345:1734-9 [PubMed]
6. Adverse effects
   1. Nausea or Vomiting
   2. Abominal pain or cramping
   3. Headache
   4. Dizziness
   5. Fatigue
   6. Insomnia
   7. Anxiety
   8. Arthralgias or myalgias
   9. Risk of lethal Opioid Overdose on relapse
      1. Decreased Opioid tolerance after use
   10. No toxicity if drinking with Naltrexone
       1. Not indicated to make them social drinkers
       2. Alcoholics tend to get less drunk on Naltrexone
   11. Very broad safety profile with minimal adverse effects
       1. However, Opioid use is a contraindication
       2. Hepatotoxicity, however is a risk
       3. Croop (1997) Arch Gen Psych 54:1130-5 [PubMed]
7. Monitoring
   1. Obtain serum liver transaminases periodically
      1. Baseline
      2. Repeat at 3 months, then every 3-6 months
8. Dosage
   1. Frequency options
      1. Daily
         1. Naltrexone 50 mg orally daily
      2. Alternate days
         1. Naltrexone 100 mg orally on Monday, Wednesday and Friday
      3. Monthly (expensive - as much as $1300 per month in 2017)
         1. Vivitrol 380 mg injection every 4 weeks (appears less effective than oral dosing)
   2. Duration
      1. May need to be used for 1 year or longer
9. Safety
   1. Pregnancy Category C
   2. Lactation: Unknown
10. References
    1. (2018) Presc Lett 25(1):5
    2. Hartmann (1997) Am Fam Physician 55(5):1877-9 [PubMed]
    3. Williams (2005) Am Fam Physician 72(9):1775-80 [PubMed]
    4. Winslow (2016) Am Fam Physician 93(6): 457-65 [PubMed]