From the Guidelines
Intrathecal morphine-induced pruritus can be effectively managed with low-dose naloxone (0.25-1 mcg/kg/hr IV infusion) as the first-line treatment, which antagonizes opioid receptors without reversing analgesia, as recommended by the most recent guidelines 1.
Treatment Options
The treatment of intrathecal morphine-induced pruritus involves several medications, including:
- Nalbuphine (5-10 mg IV every 3-4 hours), which acts as a kappa-opioid agonist and partial mu-opioid antagonist
- Ondansetron (4-8 mg IV), which shows variable efficacy
- Antihistamines like diphenhydramine (25-50 mg IV/PO every 6 hours), which may help with sedation but have limited direct effect on opioid-induced pruritus
- Low-dose propofol (10-15 mg IV bolus), which can provide rapid but temporary relief in severe cases
Mechanism and Treatment Approach
The underlying mechanism of intrathecal morphine-induced pruritus involves central mu-opioid receptor activation rather than histamine release, which explains why opioid antagonists are more effective than antihistamines 1.
Recommendations
Prophylactic administration of naloxone or nalbuphine can prevent pruritus development, and treatment should be initiated promptly to avoid significant patient distress and potential self-injury from scratching. It is essential to assess for other causes of pruritus, such as the use of other medications, before initiating treatment 1. If pruritus persists, changing to another opioid should be considered if symptomatic management has failed.
From the Research
Treatment Options for Intrathecal Morphine-Induced Pruritus
Intrathecal morphine-induced pruritus is a common side effect of intrathecal morphine administration, with a reported incidence of 58-85% 2. Several treatment options are available to manage this condition.
- Nalbuphine: Nalbuphine has been shown to be effective in preventing intrathecal morphine-induced pruritus 2, 3. A study comparing nalbuphine and ondansetron found that both drugs were effective in preventing pruritus, but nalbuphine was preferred due to its safety profile and lack of excretion in breast milk 2.
- Ondansetron: Ondansetron, a 5-HT3 receptor antagonist, has been shown to be effective in preventing and treating intrathecal morphine-induced pruritus 4, 5. A study found that ondansetron reduced the incidence and severity of pruritus compared to placebo 4.
- Dolasetron: Dolasetron, another 5-HT3 receptor antagonist, has also been shown to be effective in preventing intrathecal morphine-induced pruritus 4.
- Diphenhydramine: Diphenhydramine has been used to treat pruritus, but its effectiveness is limited compared to other options 3.
Mechanisms and Pharmacological Therapies
The mechanisms of intrathecal morphine-induced pruritus are not fully understood, but it is thought to involve the activation of central 5-hydroxytryptamine subtype 3 (5-HT3) receptors 4. A review of the current literature on neuraxial opioid-induced pruritus found that a variety of medications with different mechanisms of action have been used to manage this condition, with mixed results 6.
Comparison of Treatment Options
Studies have compared the effectiveness of different treatment options for intrathecal morphine-induced pruritus. A study found that nalbuphine was more effective than diphenhydramine in preventing epidural morphine-induced pruritus after cesarean delivery 3. Another study found that ondansetron and dolasetron were more effective than placebo in preventing intrathecal morphine-induced pruritus 4.