Treatment for Allergic Reaction with Rash to Morphine
For patients experiencing an allergic reaction with rash to morphine, immediate discontinuation of the opioid and administration of oral antihistamines is the first-line treatment, with more severe reactions requiring parenteral antihistamines, epinephrine, and potentially systemic steroids.
Initial Assessment and Management
When a patient develops a rash after morphine administration, it's crucial to determine the severity of the reaction:
Mild Reactions (Isolated Rash/Pruritus)
- Immediately discontinue morphine administration
- Administer oral antihistamines (diphenhydramine)
- Monitor vital signs and symptoms
- Observe for progression of symptoms
Moderate to Severe Reactions
- Discontinue morphine immediately
- Administer parenteral antihistamines (diphenhydramine via IM or IV route) 1
- Monitor vital signs closely (every 15 minutes until symptoms resolve)
- Position patient appropriately (recumbent with elevated lower extremities if hypotensive)
- For significant reactions, consider:
- Epinephrine (intramuscular) for systemic symptoms
- IV fluids for hypotension
- Systemic steroids for severe reactions 1
Alternative Opioid Selection
After treating the acute reaction, an alternative opioid may be needed for pain management:
- Consider switching to a synthetic opioid such as fentanyl or hydromorphone, which may be better tolerated 2, 3
- Cross-reactivity between opioids varies; naturally occurring compounds like morphine and codeine are more likely to cause allergic reactions than synthetic opioids 2
- Buprenorphine has shown good tolerance in patients with allergic reactions to other opioids 4
Special Considerations
Mechanism of Morphine Allergic Reactions
- True allergic reactions to opioids are relatively rare 2
- Morphine can cause non-allergic histamine release that mimics allergic reactions
- Some reactions may represent a true Type IV hypersensitivity mechanism 4
Monitoring and Follow-up
- Continue monitoring for at least 1-2 hours after symptoms resolve 1
- Document the allergic reaction clearly in the patient's medical record
- Consider allergy testing (patch testing) if future opioid therapy is anticipated 4
Common Pitfalls to Avoid
- Don't confuse non-allergic histamine release (common with morphine) with true allergic reactions
- Don't reintroduce morphine or closely related opioids after a confirmed allergic reaction
- Don't delay treatment of severe reactions while obtaining detailed history
- Don't use ranitidine alone for treatment (it should be combined with diphenhydramine if used) 1
Additional Interventions for Severe Reactions
For anaphylactic reactions with respiratory or cardiovascular compromise:
- Administer epinephrine immediately
- Provide supplemental oxygen
- Consider glucagon (1-5 mg IV over 5 minutes) for epinephrine-unresponsive reactions 1
- Atropine may be necessary for bradycardia
- Transfer to emergency department or intensive care unit if reaction occurs in an outpatient setting 1
By promptly recognizing and treating morphine-induced allergic reactions and selecting appropriate alternative opioids, clinicians can effectively manage these adverse events while maintaining adequate pain control.