An Allergic Reaction or Intolerance to Medication?

Case study:

A 54-year-old female patient develops a urinary tract infection while hospitalized and says she once broke out in hives after taking amoxicillin. Was that an allergic reaction or an intolerance to the medication and how should the patient be treated?

Answer:

If you aren’t sure, you’re not alone. “That’s a source of a lot of confusion,” said Dr. Kevin McConeghy, who’s part of the antimicrobial stewardship program at the University of Rhode Island College of Pharmacy. He said approximately 13% of patients admitted to VA hospitals have some sort of penicillin allergy noted in their medical records—that rate is comparable to what’s seen in community hospitals—but only a small percentage of those patients actually have a penicillin allergy when they’re tested.

That can be problematic for a number of reasons. Penicillin is the frontline therapy for a number of very common infections and patients who are labeled as allergic are excluded from taking an entire class of effective medications. Instead, they end up on second-line therapy, which are more expensive, are associated with significant side effects, and promote antibiotic resistance.

“There’s a major initiative underway in anti-microbial stewardship programs to determine if penicillin allergies are genuine, so patients are prescribed penicillin-type antibiotics instead of unnecessarily receiving second-line therapies,” said Dr. McConeghy.

For example, he pointed out, patients who had an upset stomach after taking amoxicillin did not have an allergic reaction. However, patients with a history of more serious reactions such as hives and difficulty breathing should be seen by an allergist. Dr. McConeghy said patients who report reactions to penicillin in the very distant past or reactions that were not that serious — a mild rash, for example — are candidates to undergo an oral challenge in the inpatient setting, where they can be given a dose under direct observation. 

Pharmacists are medication experts and often the frontline of patient interaction and are therefore well positioned to speak to patients who are flagged as allergic to penicillin, according to Dr. McConeghy. There are a couple hospitals in the U.S. where pharmacists and infectious disease physicians — not allergists — are flagging patients who are eligible for testing and then performing allergy tests as part of their efforts to reduce antimicrobial use. “That’s the cutting edge of antimicrobial stewardship,” he said.

Short of that level of involvement, pharmacists can talk to patients about the reactions they experienced when they took penicillin and update medical histories accordingly so providers have access to current clinical information when deciding which antibiotic is appropriate. Pharmacists can also suggest patients get tested to find out if they truly have an allergy. “Many patients don’t realize that they don’t have to go through life wondering if they’re allergic,” said Dr. McConeghy.

—Dan Cook

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