What medications should be avoided in a patient with a codeine allergy?

Medications to Avoid in Patients with Codeine Allergy

Patients with a codeine allergy should avoid all medications containing codeine as well as other naturally occurring opioids like morphine due to potential cross-reactivity and risk of serious allergic reactions. 1

Specific Medications to Avoid

Opioids to Avoid

• Codeine (in all forms and combinations)
• Morphine (naturally occurring opioid with similar structure)
• Medications containing codeine, such as:
  • Codeine-containing cough syrups
  • Combination products (e.g., codeine with acetaminophen)
  • Co-codamol
  • Tylenol with codeine

Cross-Reactivity Concerns

True allergic reactions to opioids are rare, but when they occur, there is potential cross-reactivity between naturally occurring opioids that share similar chemical structures 2. The risk is highest with:

• Morphine (highest risk of cross-reactivity)
• Other naturally derived opioids

Safer Alternative Medications

For Mild to Moderate Pain

• Acetaminophen (Tylenol) - first-line alternative
• NSAIDs (if not contraindicated):
  • Ibuprofen
  • Naproxen
  • Celecoxib (for patients with NSAID sensitivities)

For Moderate to Severe Pain

• Synthetic opioids (generally safer in codeine allergy):
  • Fentanyl - preferred option 1
  • Hydromorphone - good alternative 1
  • Oxycodone - use with caution and monitoring
  • Buprenorphine - alternative option

Special Considerations

• Tramadol should be used with caution as it has a different structure but carries other risks including seizures and serotonin syndrome 3
• Meperidine is not recommended due to poor efficacy, multiple drug interactions, and increased risk of toxicity 1

Clinical Decision-Making Algorithm

1. Confirm true codeine allergy:

   • Distinguish between true allergy (urticaria, anaphylaxis) and adverse effects (nausea, constipation)
   • Document reaction details and severity

2. For mild pain:

   • Start with acetaminophen (up to 3g/day)
   • Add NSAIDs if not contraindicated

3. For moderate to severe pain:

   • Use synthetic opioids (fentanyl, hydromorphone preferred)
   • Avoid naturally occurring opioids

4. For patients requiring long-term pain management:

   • Consider pain specialist referral
   • Explore multimodal pain management strategies

Important Monitoring Considerations

• Monitor closely for signs of allergic reaction with first dose of any alternative opioid
• Start with lower doses when using synthetic opioids in patients with history of severe codeine allergy
• Document codeine allergy prominently in patient's medical record and alert pharmacy

Special Populations

• Patients with renal impairment: Avoid morphine, codeine, and meperidine due to accumulation of active metabolites 1
• Elderly patients: Use additional caution with all opioids due to increased risk of respiratory depression 1
• Patients with liver disease: Prefer fentanyl, buprenorphine, or hydromorphone; avoid codeine 4

Remember that while synthetic opioids are generally safer in patients with codeine allergy, any medication can potentially cause an allergic reaction, so careful monitoring with the first dose of any alternative analgesic is essential.