From the Guidelines
The chemical class of an opioid, such as phenanthrene, phenylpiperidine, or phenylheptane, does not significantly impact the risk of allergic reaction in a patient allergic to one opioid, as true allergic reactions are rare and not typically class-specific. When considering the management of pain in patients with a history of opioid allergy, it's crucial to understand that the chemical structure of the opioid (e.g., phenanthrene, phenylpiperidine, or phenylheptane) does not reliably predict cross-reactivity 1.
Key Considerations
- True allergic reactions to opioids are rare and generally not class-specific, meaning a patient allergic to one opioid could potentially tolerate another from a different chemical class.
- Cross-reactivity can occur, particularly among opioids within the same chemical class, such as among phenanthrenes (e.g., morphine, codeine, hydromorphone).
- If a patient has experienced a true allergic reaction to an opioid, using an opioid from a different chemical class is recommended, such as switching from morphine (a phenanthrene) to fentanyl (a phenylpiperidine) 1.
- It's essential to distinguish between true allergic reactions (involving immune system activation) and common opioid side effects (predictable pharmacological effects), as the latter may occur with any opioid regardless of its chemical class.
Clinical Implications
- For patients with a history of opioid allergy, selecting an opioid from a different chemical class can be a safe strategy to manage pain while minimizing the risk of an allergic reaction.
- Fentanyl, being a phenylpiperidine, is noted for its quicker onset of action and higher potency compared to morphine, a phenanthrene, and may be considered for patients allergic to morphine 1.
- The choice of opioid should be guided by the patient's specific needs, the severity of their pain, and their medical history, rather than solely by the chemical class of the opioid.
From the FDA Drug Label
Fentanyl transdermal system is contraindicated in patients with known hypersensitivity to fentanyl or any components of this product. The FDA drug label does not answer the question.
From the Research
Opioid Allergy and Chemical Class
- The chemical class of an opioid, such as phenanthrene, phenylpiperidine, or phenylheptane, does not appear to significantly affect the risk of allergic reaction in a patient allergic to one opioid 2, 3.
- Studies have shown that the incidence of opioid allergy cross-reactivity is low, with cross-reactivity rates ranging from 0% to 6.7% 2.
- A retrospective study found that patients with previously documented opioid allergy or adverse drug reaction (ADR) to one opioid class could tolerate subsequent exposure to opioids from different classes, with no cross-reactivity found among any of the opioid drug classes 3.
Allergic Reactions to Opioids
- True allergic reactions to opioids are rare, and most adverse reactions can be attributed to side effects or pseudo-allergies 4, 5.
- Allergic reactions to opioids can range from mild to severe, and proper diagnosis and management are essential to prevent unnecessary avoidance of opioids and ensure patient safety 4, 5.
- Drug provocation testing (DPT) is considered the gold standard for diagnosing opioid allergy, but its use is limited, and further studies are needed to evaluate its effectiveness 5.
Clinical Implications
- The low likelihood of true reactivity to opioids, combined with the potential clinical relevance of an opioid allergy label, calls for further characterization of this label in populations with acute or chronic pain diagnoses 5.
- Removing erroneous opioid allergy labels is crucial to ensure that patients receive appropriate pain management and to prevent unnecessary avoidance of opioids 5.
- Clinicians should be aware of the limitations of opioid allergy labels and use a systematic approach to evaluate and manage patients with suspected opioid allergies 2, 5.