Pregnant women safely tolerate amoxicillin direct oral challenges

Pregnant women with a history of penicillin allergy safely passed direct oral challenges for amoxicillin without preceding skin testing, according to a study published in The Journal of Allergy and Clinical Immunology: In Practice.

“Penicillin allergy delabeling in low-risk patients has been shown to be safe and effective in other patient populations,” Raymond Mak, MD, FRCPC, clinical instructor in the division of allergy and immunology in the department of medicine at University of British Columbia in Vancouver, told Healio.

Testing reveals that more than 90% of patients truly are not allergic, Mak said. Yet pregnant women often are excluded from most studies, he added, even though pregnancy does not make them more likely to be allergic to penicillin.

“Many health care professionals are fearful of testing pregnant women, by virtue of them being pregnant,” Mak said. “At our center, almost 50% of women will need an antibiotic during their pregnancy, and having an unverified label can lead to suboptimal prescribing practices.”

Clinicians at the BC Women’s Hospital and Health Centre administered direct oral challenges to 207 pregnant women who were 28 to 36 weeks’ gestation between July 2019 and September 2021. These women all were deemed very low risk based on having a PEN-FAST score of 0, a validated, point-of-care penicillin allergy clinical decision tool that predicts the chances of positive skin tests.

History indicated 77% had experienced reactions to penicillin more than 10 years before, with 49% of these reactions involving a maculopapular rash, and 20.3% of these rashes lasting less than 24 hours.

After receiving 500 mg of amoxicillin orally, these women were monitored for an hour. Clinicians recorded their vital signs at baseline and then 15 minutes and an hour after ingestion. Patients with no signs of IgE-mediated reactions were discharged and told to call the clinic if they had any concerns about a delayed reaction.

According to the researchers, 203 of these patients reported no immediate or delayed hypersensitivity. The other four patients (1.93%) experienced benign maculopapular rashes that were treated with betamethasone valerate 0.1% ointment and oral antihistamines.

The researchers said the 1.93% reaction rate was similar to a previously reported 1.99% rate among a nonpregnant adult population and a previously reported 2.5% rate among a pregnant population.

None of the patients required epinephrine or experienced anaphylaxis, nor were any admitted to the hospital due to complications from the testing.

“Tests for penicillin allergy can be done during pregnancy,” Mak said. “Proactively removing these unverified labels can provide benefits during this pregnancy and beyond.”

The researchers also concluded that non-allergists can safely conduct direct oral challenges for pregnant women, which would increase access to penicillin allergy assessment when allergists are not readily available.

“Many centers are still hesitant to offer penicillin allergy assessments to pregnant women,” Mak said. “Hopefully, this will provide them with confidence to extend this service.”

Also, the researchers said the reduced need for penicillin skin testing would lower the costs associated with reagents, clinic time and the need to see a subspecialist, which in turn would significantly improve patient care during labor and delivery.

“We are looking at the overall long-term cost savings and outcomes in immediate and long-term antimicrobial prescription practices,” Mak said. “We have implemented a point-of-care bedside assessment tool that can be used by non-allergists to risk-stratify patients. We hope to compare the recommendations of this tool with allergists' assessments.”

For more information:

Raymond Mak, MD, FRCPC, can be reached at raymondtmak@yahoo.com.