Can you take nalrexone (naltrexone) while on opioids?

Naltrexone Should Not Be Taken While on Opioids Due to Risk of Precipitated Withdrawal

Taking naltrexone while on opioids is contraindicated as it will precipitate severe opioid withdrawal symptoms that can be potentially life-threatening. 1

Mechanism and Risks

Naltrexone is a competitive opioid antagonist that blocks opioid receptors. When administered to someone with opioids in their system:

• It rapidly displaces opioids from receptors, causing sudden and severe withdrawal symptoms
• Withdrawal symptoms can begin within minutes to hours of taking naltrexone
• The severity of withdrawal is typically more intense than natural withdrawal

Clinical Manifestations of Precipitated Withdrawal

Common symptoms include:

• Severe agitation (occurs in 96.2% of cases) 2
• Altered consciousness (38.6%)
• Nausea (28%) and vomiting (27.3%)
• Abdominal pain (24.2%)
• Diarrhea (16.7%)
• Bone and muscle pain (15.9%)
• Tachycardia (12.9%)
• Dilated pupils (11.4%)

In severe cases, this can lead to:

• Dehydration
• Electrolyte imbalances
• Cardiovascular instability
• Potentially life-threatening complications

Required Opioid-Free Period

Before starting naltrexone:

• Patients must be completely opioid-free for a minimum of 7-10 days 1
• For long-acting opioids like methadone, a longer opioid-free period may be required
• A naloxone challenge test should be performed if there is uncertainty about opioid clearance 1

Special Considerations

For patients with opioid use disorder who wish to transition to naltrexone:

• Complete medically supervised detoxification first
• Verify opioid-free status through both urine drug screening and naloxone challenge
• Initial oral naltrexone dose should be 25 mg for 1-3 days to assess tolerability before increasing to the standard 50 mg daily maintenance dose 3

Emergency Management of Accidental Co-administration

If naltrexone is accidentally taken while on opioids:

• Immediate medical attention is required
• Treatment typically involves:
  • Sedation (often with benzodiazepines)
  • Management of vomiting and diarrhea
  • IV fluids for dehydration
  • Supportive care for symptoms 4
  • High-dose buprenorphine may be considered in some cases 5

Alternative Approaches

For patients currently on opioids who require treatment for substance use disorders:

• Buprenorphine/naloxone is a first-line treatment that can be initiated while in mild-moderate withdrawal 3
• Methadone maintenance is another option that doesn't require complete opioid abstinence

Conclusion

The FDA drug label for naltrexone explicitly warns against its use in patients currently taking opioids due to the risk of precipitated withdrawal. This contraindication applies to both therapeutic opioid use and opioid use disorder. The opioid-free period must be strictly observed to prevent potentially dangerous withdrawal reactions.