What medications are used to treat opiate-induced itching?

Management of Opioid-Induced Pruritus

Antihistamines such as diphenhydramine (25-50 mg IV/PO every 6 hours) or promethazine (12.5-25 mg PO every 6 hours) should be used as first-line treatment for opioid-induced pruritus. 1

First-Line Approach

When a patient presents with opioid-induced itching, follow this algorithm:

1. Rule out other causes of pruritus

   • Check for other medications that may cause itching
   • Assess for underlying skin conditions or systemic diseases 1

2. First-line pharmacological management:

   • Antihistamines:
     • Diphenhydramine 25-50 mg IV or PO every 6 hours
     • Promethazine 12.5-25 mg PO every 6 hours 1

Second-Line Options

If pruritus persists despite antihistamine therapy:

1. Consider opioid rotation:

   • Switch to a different opioid if symptomatic management has failed
   • Some opioids (like hydromorphone) may cause less itching than others (like morphine) in certain patients 2

2. Add a mixed opioid agonist-antagonist:

   • Nalbuphine 0.5-1 mg IV every 6 hours as needed
   • This is particularly effective for neuraxial opioid-induced pruritus without attenuating analgesia when used at low doses (25-50% of analgesic dose) 1, 3

3. Consider low-dose naloxone infusion:

   • Continuous infusion of naloxone at 0.25 mcg/kg/hour
   • Titrate up as needed for relief of pruritus
   • This approach can relieve itching without decreasing analgesic effectiveness 1

Mechanism and Special Considerations

Opioid-induced pruritus occurs through multiple mechanisms:

• Histamine release from mast cells (peripheral mechanism)
• Direct central nervous system effects via μ-opioid receptors
• Possible involvement of serotonin pathways 4

The incidence varies by administration route:

• Higher with neuraxial (spinal/epidural) administration (up to 46% with spinal opioids)
• Lower with oral or IV administration (2-10%) 1, 5

Important Clinical Pearls

• Antihistamines may cause sedation, which can compound opioid-induced sedation. Monitor patients closely, especially the elderly.
• Nalbuphine has shown superior efficacy compared to diphenhydramine, naloxone, and propofol for treating opioid-induced pruritus, particularly with neuraxial opioids 3
• Low-dose naloxone infusion can effectively treat pruritus without reversing analgesia, but requires careful titration 1
• Opioid rotation may be effective when a patient experiences severe itching with one opioid but not another 2

Treatment-Resistant Cases

For severe or persistent pruritus despite the above measures:

1. Consider adding a serotonin antagonist like ondansetron, though evidence is mixed 1
2. Evaluate for alternative pain management strategies to reduce opioid requirements
3. Consider neuraxial analgesics or neuroablative techniques if appropriate to reduce opioid dose 1

Remember that opioid-induced pruritus often does not respond to conventional antipruritic treatments, making a targeted approach using the medications discussed above essential for effective management.