The Hospice Clinician Blog

Hospice patients may report allergies to opioids, but often these are pseudoallergies consisting of symptoms of itching, flushing and sweating. Pseudoallergy type reactions are relatively common.

True allergy to opioids is rare. (1) Pseudoallergy is caused by release of histamine from the mast cells in the skin, a non-immunologic event. (2) True allergy is believed to be IgE mediated or T-cell mediated. (3) If the reaction is only flushing, itching, or sweating the opioid can often be continued with the addition of an antihistamine or dose reduction. (4) If the true nature of the reaction to an opioid is not clarified, the hospice patient may be incorrectly "labeled" as allergic to opioids and opioid drugs may be withheld unnecessarily.

If the reaction consists of hives, increased heart rate, severe hypotension, or bronchospasm the patient should be assumed to be exhibiting a true allergic reaction and the clinician will need to decide which, if any, opioid is safe for the hospice patient.

Codeine, Morphine, and Meperidine are associated with the most allergictype reactions. (1) It has been suggested that hospice patients allergic to one opioid are less likely to react to an opioid in a different structural class.

It is reasonable to consider rotating from an opioid from one class to one from another distinct class in some situations. The 3 main structural classes are as follows:

• Morphine group: morphine, codeine hydrocodone, oxycodone, oxymorphone, hydromorphone, levorphanol

• Diphenylheptanes: methadone, propoxyphene

• Phenylpiperidines: fentanyl, meperidine

Some patients may experience localized itching and redness underneath the Fentanyl patch. Patch site rotation is very important to reduce this risk. This reaction can be managed by topical application of a steroid, such as triamcinolone spray prior to application of the patch.

Although many hospice patients may report a history of allergy to opioids, most have only experienced a side effect . Proper selection of an opioid medication based upon past history can result in significantly improved outcomes in pain management for the hospice patient.

(1) J Oncol Pharm Practice 2004;10: 177-82 (2) Immunol Allergy Clin North Am 1991;111: 635-44 (3) Anesthesiology 1989; 71: 489-94 (4) Applied Therapeutics: The Clinical Use of Drugs 8th ed. 2005

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