Ondansetron for Opioid-Induced Pruritus
Efficacy of Ondansetron
- 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, 4
- The British Association of Dermatologists' guidelines state that 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, 2, 3
- 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, 3
Recommended Treatment Algorithm
- Antihistamines such as diphenhydramine or promethazine are recommended as initial treatment by the National Comprehensive Cancer Network 5, 6, 7
- Assess for other causes of pruritus, as pruritus is more likely to occur early in the course of opioid treatment 5, 6
- Opioid antagonists have proven useful when antihistamines fail 5, 6
- Mixed agonist/antagonists (e.g., nalbuphine) can be used to treat opioid-induced pruritus 5, 6
- μ-opioid receptor antagonists (e.g., naloxone, naltrexone) can be used with careful dose titration to produce relief without reversing analgesic efficacy 5, 6, 8
- Methylnaltrexone (a peripheral opioid antagonist with reduced ability to cross the blood-brain barrier) can be considered 1, 8
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, 5
- The British Association of Dermatologists' guidelines do not support the routine use of ondansetron for opioid-induced pruritus despite its efficacy for opioid-induced nausea 1, 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, 3
- Avoid using full doses of opioid antagonists in opioid-dependent patients as this may precipitate withdrawal 5, 6
- Don't overlook other causes of pruritus in patients receiving opioids, such as other medications or underlying skin conditions 5, 6