Opioids and Allergies

Hospice patients often communicate allergies to medications.  When the medication is an opioid, hospice staff often have to determine whether the reaction that the patient believed to be an allergy is truly an allergy and whether the reaction necessitates the avoidance of certain opioids.  True allergies involve an immune response; other reactions can fall into the category of either side effects or pseudoallergy, which is generally the result of histamine release but no actual immune response.  Given a patient’s reaction history, sometimes it can be difficult to determine which medications are safe and which are not, but some simple collection of reaction information can provide some guidance.

Pseudoallergy: If the following symptoms occur with respect to opioid administration, they are likely related to a pseudoallergy rather than a true drug allergy:

• Generalized flushing, itching, and/or sweating
• Mild hypotension
• Itching, flushing, or hives at injection/application site

Such reactions can be managed with the following:

• Try nonopioid analgesics for mild pain
• Avoid codeine, morphine, and meperidine
• Use a more potent opioid at appropriate doses (drugs listed below from least to most potent):
  • Meperidine < codeine < morphine < hydrocodone < oxycodone < hydromorphone  < fentanyl
• If opioid in question is effective against pain and symptoms are mild, consider administering it with an antihistamine
• Consider a reduction in dose, if tolerated
• Avoid parenteral administration and/or slow down the rate of administration

Allergy: A true allergy to an opioid often displays one or more of the following:

• Bronchospasm
• Breathing, speaking, and/or swallowing difficulties
• Angioedema
• Severe hypotension
• Urticaria

When there is a history of such symptoms related to a certain opioid:

• Do not administer the offending agent
• Try a nonopioid analgesic if pain is mild
• Try an opioid from a different chemical class and monitor closely (see below for general opioid drug classes)