Ondansetron (Zofran) for Opioid-Induced Pruritus
Ondansetron is not recommended as a first-line treatment for opioid-induced pruritus as it does not reduce the incidence of pruritus compared to placebo, though it may reduce severity in some cases. 1
Efficacy of Ondansetron for Opioid-Induced Pruritus
- Opioid-induced pruritus is common, affecting 2-10% of patients receiving oral opioids, 10-50% receiving intravenous opioids, and 20-100% receiving epidural or intrathecal opioids 1
- According to the British Association of Dermatologists' guidelines, ondansetron and other 5-HT3 receptor antagonists do not reduce the incidence of opioid-induced pruritus or time to onset when compared with placebo 1
- While some evidence suggests ondansetron 4 mg or 8 mg may reduce the severity or need for treatment of pruritus secondary to opiates, this has been refuted in more recent studies 1
Recommended Treatment Algorithm for Opioid-Induced Pruritus
First-line options:
- Antihistamines such as diphenhydramine or promethazine are recommended as initial treatment 2
- Assess for other causes of pruritus, as pruritus is more likely to occur early in the course of opioid treatment 2
Second-line options (if antihistamines fail):
- Opioid antagonists have proven useful when antihistamines fail 2
- Mixed agonist/antagonists (e.g., nalbuphine) can be used to treat opioid-induced pruritus 2, 3
- μ-opioid receptor antagonists (e.g., naloxone, naltrexone) can be used with careful dose titration to produce relief without reversing analgesic efficacy 2, 4
- Methylnaltrexone (a peripheral opioid antagonist with reduced ability to cross the blood-brain barrier) can be considered 1, 4
Third-line options:
- Consider opioid rotation if pruritus persists despite symptomatic management 2
- Diclofenac 100 mg rectally has shown efficacy in reducing postoperative pruritus 1, 4
- Mirtazapine 30 mg daily orally or gabapentin 1200 mg daily in divided doses have shown efficacy in preventing morphine-induced pruritus in surgical settings 1, 4
Important Clinical Considerations
- The use of opioid antagonists in treating opioid-induced pruritus risks inducing significant pain by reversing analgesia, requiring careful dose titration 1, 2
- Pruritus is particularly common with neuraxial (epidural and intrathecal) opioid administration 5
- While some small studies have reported success with ondansetron for opioid-induced pruritus 6, 7, the highest quality evidence from guidelines does not support its routine use 1
- Intranasal butorphanol has shown promise in small studies for treating opioid-induced pruritus unresponsive to antihistamines 3
Common Pitfalls to Avoid
- Do not rely on ondansetron as a first-line treatment for opioid-induced pruritus despite its efficacy for opioid-induced nausea 1
- Avoid using full doses of opioid antagonists in opioid-dependent patients as this may precipitate withdrawal 2
- Don't overlook other causes of pruritus in patients receiving opioids, such as other medications or underlying skin conditions 2
- Remember that pruritus can be so severe that it may require modification or abandonment of opioid therapy if unresponsive to treatment 3, 8