Management of Pruritus After Spinal Morphine in a Patient Already on Cetirizine
Since cetirizine has already failed, immediately switch to nalbuphine 2.5-5 mg IV as the first-line treatment for neuraxial opioid-induced pruritus. 1, 2
Why Cetirizine Is Not Working
Antihistamines like cetirizine are ineffective for opioid-induced pruritus because this type of itching is mediated primarily through μ-opioid receptors in the central nervous system, not through histamine release. 3 While cetirizine works well for urticaria and atopic dermatitis 4, it does not address the mechanism of neuraxial morphine-induced pruritus. 5
Recommended Treatment Algorithm
First-Line: Nalbuphine (Mixed Agonist-Antagonist)
- Administer nalbuphine 2.5-5 mg IV every 6 hours as needed for immediate relief of pruritus. 3
- This low dose (25-50% of the analgesic dose) effectively treats pruritus without reversing analgesia or increasing sedation. 1
- Nalbuphine is superior to diphenhydramine, naloxone, and propofol for neuraxial opioid-induced pruritus, with the highest efficacy among all studied agents. 1, 2
- In a randomized controlled trial, prophylactic nalbuphine 10 mg IM reduced pruritus incidence from 72% to 44% and significantly decreased severity at 4 and 12 hours postoperatively compared to diphenhydramine. 2
Second-Line: Low-Dose Naloxone Infusion
- If nalbuphine is unavailable or ineffective, start a continuous naloxone infusion at 0.25 mcg/kg/h and titrate up to 1 mcg/kg/h. 3
- This ultra-low dose provides pruritus relief without reversing the analgesic effect of spinal morphine. 3, 5
- Critical pitfall: Higher doses of naloxone will reverse analgesia, so careful titration is essential. 3
Third-Line: Consider Opioid Rotation
- If pruritus persists despite nalbuphine or naloxone, change to an alternative opioid for ongoing pain management. 3
- Pruritus occurs in 10-50% of patients receiving opioids and is more common with neuraxial administration. 3, 5
What NOT to Do
- Do not continue or increase cetirizine – it will not work for opioid-induced pruritus. 3
- Do not use diphenhydramine or other sedating antihistamines except in palliative care settings, as they are less effective than nalbuphine and carry risks of sedation, falls, and potential long-term dementia risk. 3, 6
- Do not use serotonin antagonists (ondansetron, granisetron) – these are for opioid-induced nausea, not pruritus. 3
Important Clinical Considerations
- Pruritus from neuraxial morphine typically occurs early in the course of treatment and is most common within the first 24 hours. 3
- The mechanism involves μ-opioid receptor activation in the central nervous system, with possible contributions from serotonin and dopamine pathways. 5
- Assess for other causes of pruritus (other medications, allergic reactions, skin conditions) before attributing it solely to morphine. 3
- Nalbuphine may also provide the added benefit of reducing nausea/vomiting and reversing mild respiratory depression if present. 1