Don’t fear testing for, and delabeling, penicillin allergy

The oral amoxicillin challenge

After patients take a treatment dose of oral amoxicillin, they should be observed for 1 hour for any objective reaction. The clinical setting should be able to support patients in the rare case of a more severe reaction to penicillin. Subjective symptoms such as pruritus without objective findings such as rash may be considered a successful challenge, and penicillin may be taken off the list of allergies. The treating team can bill CPT codes for drug challenge testing.

Some research has supported multidose testing with amoxicillin to assess for late reactions to a penicillin oral challenge, but the current guidelines recommend against this approach based on the very limited yield in finding additional cases of true allergy with extra doses of antibiotics. One method to address this issue is to have patients advise the practice if symptoms develop within 10 days of the oral challenge, with photos or prompt clinical evaluation to assess for an IgE-mediated reaction.

Many patients, and certainly some clinicians, will have significant trepidation regarding an oral challenge, despite the low risk for complications. For these patients, as well as children with a history of penicillin allergy and patients with a history of anaphylaxis to penicillin or probable IgE-mediated reaction to penicillin in the past several years, skin testing is recommended. Lower-risk patients might feel reassured to complete an oral challenge test after a negative skin test.

Penicillin skin testing is more reliable than a radioallergosorbent test or an enzyme-linked immunoassay and carries a high specificity. However, skin testing requires the specialized care of an allergy clinic, and this resource is limited in many communities.

Many patients will have negative oral challenge or skin testing for penicillin allergy, but there are still some critical responsibilities for the clinician after testing is complete. First, the label of penicillin allergy should be expunged from all available health records. Second, the clinician should communicate clearly and with empathy to the patient that they can take penicillin-based antibiotics safely and with confidence. Repeat testing is unnecessary unless new symptoms develop.

Given the millions of U.S. residents with penicillin allergy documented in the health record but limited resources for allergy testing, we all need to be engaged in proactively delabeling this allergy from patients who can take penicillin antibiotics without problems. But the application of this policy to clinical practice is challenging on several levels, from patient and clinician fear to practical constraints on time.

Dr. Vega is health sciences clinical professor, family medicine, University of California, Irvine. He has disclosed ties with McNeil Pharmaceuticals.

A version of this article originally appeared on Medscape.com.