Can patients with a codeine allergy take oxycodone?

Opioid Selection for Patients with Codeine Allergy

Patients with a codeine allergy can safely take oxycodone as there is minimal cross-reactivity between these opioid classes. 1, 2

Understanding Opioid Classes and Cross-Reactivity

Opioids can be categorized into different classes based on their chemical structure:

• Natural opioids: Morphine, codeine
• Semi-synthetic opioids: Oxycodone, hydrocodone, hydromorphone
• Synthetic opioids: Fentanyl, methadone

Cross-Reactivity Data

Recent evidence shows extremely low rates of cross-reactivity between different opioid classes:

• A comprehensive retrospective study found 100% tolerance rates when patients with documented opioid allergies were exposed to opioids from different classes 1
• Another study found cross-reactivity rates between opioid classes ranging from only 0% to 6.7%, with 92.5% of patients successfully tolerating readministration of opioids despite chart-documented allergies 2

Differentiating True Allergies from Adverse Reactions

It's important to note that true IgE-mediated allergic reactions to opioids are rare:

• Approximately 50% of documented "opioid allergies" are actually intolerances (side effects) rather than true allergic reactions 2
• Common opioid side effects that may be misinterpreted as allergies include:
  • Nausea/vomiting
  • Pruritus (itching)
  • Respiratory depression
  • Sedation

Safe Opioid Selection for Patients with Codeine Allergy

Recommended Options:

1. Oxycodone: First-line alternative for patients with codeine allergy

   • Available in immediate and extended-release formulations 3
   • Can be used alone or in combination with acetaminophen 3
   • Initial dosing: 5-15 mg PO every 4-6 hours as needed 3

2. Hydromorphone: Alternative option if oxycodone is unavailable

   • Initial dosing: 2-4 mg PO every 4-6 hours as needed 3
   • Use with caution in renal impairment 4

3. Fentanyl: For severe pain requiring parenteral administration

   • Preferred option in patients with renal impairment 4
   • Less histamine release compared to natural opioids 5

Cautions and Special Considerations:

• CYP2D6 metabolism: Codeine requires CYP2D6 metabolism to produce morphine for analgesic effect. Patients who are poor metabolizers may have reduced response to codeine but can still respond to oxycodone, though possibly at altered effectiveness 6

• Renal impairment: If the patient has renal impairment:

  • Avoid morphine and codeine 4
  • Consider fentanyl or buprenorphine as safer alternatives 4
  • If using hydromorphone, start with 25-50% of normal dose 4

Clinical Approach to Patients with Reported Codeine Allergy

1. Assess the nature of the previous reaction:

   • Symptoms suggestive of true allergy: urticaria, angioedema, bronchospasm, hypotension
   • Symptoms suggestive of intolerance: nausea, vomiting, constipation, sedation

2. Document the specific reaction:

   • Avoid vague terms like "allergy" without specific symptoms
   • Document timing, severity, and management of previous reaction

3. Select appropriate alternative:

   • For true allergic reactions to codeine: oxycodone is generally safe
   • For intolerances: consider addressing the specific side effect (e.g., antiemetics for nausea)

Common Pitfalls to Avoid

• Overestimating cross-reactivity: Assuming all opioids will cause reactions in patients with codeine allergy
• Underprescribing analgesia: Inadequate pain management due to fear of allergic reactions
• Mislabeling intolerances as allergies: Leading to unnecessary restrictions in pain management options
• Escalating to stronger opioids unnecessarily: Patients with codeine allergy being prescribed high-potency opioids like fentanyl when intermediate options would be appropriate 5

By understanding the low risk of cross-reactivity between opioid classes and differentiating between true allergies and intolerances, clinicians can safely and effectively manage pain in patients with codeine allergy using alternative opioids like oxycodone.