From the Guidelines
Morphine is not a suitable alternative for individuals with a codeine allergy due to the risk of cross-reactivity and potential for severe allergic reactions. Both morphine and codeine are opioids, and their similar chemical structures increase the likelihood of an allergic response to morphine in individuals allergic to codeine 1. The study published in Critical Care in 2013 highlights the importance of careful analgesic selection, particularly in patients with known allergies, and suggests alternative opioids like hydromorphone for patients with type 2 allergies to morphine, but does not directly address codeine allergy 1. Key considerations in managing pain for someone with a codeine allergy include:
- Avoiding opioids with similar structures to codeine, such as morphine, to minimize the risk of cross-reactivity
- Exploring non-opioid pain management options, such as acetaminophen or NSAIDs, which may be safer alternatives
- Consulting with an allergist or healthcare provider to determine the best pain management strategy based on individual medical history and allergies. The evidence from 1 supports the use of alternative analgesics but emphasizes the need for a tailored approach to pain management, especially in patients with known allergies.
From the Research
Morphine and Codeine Allergy
- Morphine is a commonly used analgesic agent, but its use in patients with a codeine allergy is not well-established 2.
- Codeine and morphine are both opioids, but they have different chemical structures and mechanisms of action.
- There is limited evidence on the cross-reactivity between codeine and morphine, but some studies suggest that it is low 3, 4.
Opioid Allergy Cross-Reactivity
- A retrospective study found no cross-reactivity among patients with previously documented opioid allergy or adverse drug reaction across three opioid classes, including natural, semisynthetic, and synthetic opioids 3.
- Another study found that the risk of IgE-mediated reactions caused by opioids is low in patients with historical IgE-mediated reactions to opioids, with cross-reactivity rates ranging from 0% to 6.7% 4.
- These findings suggest that morphine may be safe to use in patients with a codeine allergy, but more research is needed to confirm this.
Clinical Implications
- The removal of erroneous opioid allergy labels is important in patients with acute or chronic pain, as it can lead to the use of alternative opioids with less histamine release 5.
- Clinicians should carefully evaluate patients with reported opioid allergies and consider the use of alternative opioids, such as morphine, if necessary.
- Further research is needed to determine the safety and efficacy of morphine in patients with a codeine allergy.