Why Was There Ever a Warning Not to Use Cephalosporins in the Setting of a Penicillin "Allergy"?

Advances in the Understanding of Drug Hypersensitivity: 2012 Through 2022

Over the last decade there have been key advances in understanding mechanisms, risk, and consequences of both true immunological drug hypersensitivity and unverified drug allergy labels that have changed clinical practice. This has been facilitated by the widespread adoption of electronic health records (EHRs). The vast majority of EHR drug allergy labels are unverified and cause significant morbidity from unnecessary avoidance of optimal drug therapy. There has also been significant movement in our understanding of mechanisms of drug hypersensitivity that, in addition to advancing our understanding of the pathogenesis of immediate and delayed reactions, have guided preventive efforts, diagnostic procedures, and clinical management. More widespread adoption, including scale-up of "allergy" delabeling and appropriate management, specifically for antibiotics, opiates, radiocontrast, chemotherapeutics, biologics, and nonsteroidal anti-inflammatory medications, will be necessary to improve patient outcomes over the next decade. This will require further engagement and collaboration between primary care health care providers, allergists, and other specialists.

Adherence and outcomes of a surgical prophylaxis guideline promoting cephalosporin use among patients with penicillin allergy

BACKGROUND

The study purpose was to assess adherence to a local surgical prophylaxis guideline in patients with reported penicillin allergies, which recommends cephalosporins as first-line prophylaxis.

METHODS

Adult patients with penicillin allergies admitted for a surgical procedure from July 2020 to June 2021 were retrospectively screened, and the first surgery per admission was included. The primary outcome was the proportion of surgeries using β-lactam prophylaxis. Additional outcomes included prophylaxis timing, hypersensitivity reactions, acute kidney injury, infectious complications, duration of stay, and 30-day mortality or readmission.

RESULTS

Among 597 procedures, 504 patients (84.4%) received a β-lactam for surgical prophylaxis, including 494 (82.3%) who received a cephalosporin. Patients in the non-β-lactam group were more likely to have a type I IgE-mediated penicillin allergy (48.4% vs 31.7%, P = .002); however, the majority with type I reactions still received β-lactams (78.0%), including in the setting of anaphylaxis or angioedema to penicillin (67.7%). Zero allergic reactions to prophylaxis antibiotics were reported in either group, and there were no significant differences in the proportion of patients receiving drugs associated with the management of allergic reactions. Receipt of non-β-lactams was associated with inappropriate prophylaxis timing (9.7% vs 3.2%, P = .005) and postprocedural acute kidney injury (7.5% vs 0.6%, P < .001). All other outcomes were nonsignificant between the groups.

CONCLUSION

Among surgical patients with a documented penicillin allergy, most received cephalosporin prophylaxis as recommended by institutional guidelines, with zero allergic reactions. Receipt of non-β-lactam prophylaxis was associated with worsened outcomes. Cephalosporin prophylaxis should be preferred for surgical patients, including in the setting of true penicillin allergy.

Improving Intrapartum Group B Streptococcus Prophylaxis in Patients with a Reported Penicillin or Cephalosporin Allergy: A Quality Improvement Project

OBJECTIVE

To evaluate the impact of a standardized allergy-guided approach to Group B Streptococcus (GBS) prophylaxis in pregnant women with reported penicillin or cephalosporin allergy.

METHODS

This interrupted time-series analysis included obstetric patients requiring GBS prophylaxis who reported penicillin or cephalosporin allergies. Patients were divided into baseline (April 1, 2019 to July 21, 2020) and intervention (July 22, 2020 to July 31, 2021) groups. The primary outcome was prophylaxis appropriateness, based on antibiotic type, nature of reaction, and cross-reactivity risk. Secondary outcomes included type of prophylaxis received and antibiotic-related adverse events.

RESULTS

The study included 88 patients in the baseline period and 52 patients in the intervention period. Appropriate prophylaxis increased from 47% (41/88) to 85% (44/52), with the segmented regression model confirming a statistically significant increase over time (incidence rate ratio 1.57; 95% CI 1.02-2.43, P = 0.04, slope coefficient 1.06/month; 95% CI 1.01-1.10, P = 0.01). Penicillin and cefazolin use increased from 61% (54/88) to 87% (45/52) in the intervention period (P = 0.002), and no hypersensitivity reactions occurred during this period.

CONCLUSIONS

Implementation of standardized allergy-guided prophylaxis safely improved appropriate β-lactam antibiotic use in obstetric patients requiring GBS prophylaxis who reported penicillin and cephalosporin allergies.

Population-Based Incidence of New Ampicillin, Cephalexin, Cefaclor, and Sulfonamide Antibiotic "Allergies" in Exposed Individuals with and without Preexisting Ampicillin, Cephalexin, or Cefaclor "Allergies"

BACKGROUND

There is a theoretical concern, unconfirmed by population-based challenge data, that clinically significant, immunologically mediated hypersensitivity occurs among β-lactams sharing side chains.

OBJECTIVE

To determine the population-based allergy incidence associated with the use of β-lactams sharing exact R1 side chains (ampicillin, cephalexin, and cefaclor [ACC]), with or without a current ACC allergy or a sulfonamide antibiotic allergy for comparison.

METHODS

All courses of ACC and trimethoprim-sulfamethoxazole used by any Kaiser Permanente California members in 2017 and 2018, with follow-up through January 2019, were identified along with their preexisting antibiotic allergy status and all new antibiotic-specific allergies reported within 30 days of course initiation.

RESULTS

A total of 1,167,713 courses of ACC were administered to individuals. No sulfonamide antibiotic or ACC allergy and 4771 new ACC allergies (0.41%) were reported. Moreover, 130,032 courses of ACC were administered to individuals with a sulfonamide antibiotic allergy; no ACC allergy and 904 new ACC allergies (0.70%) were reported. There were 5,958 courses of ACC administered to individuals with an ACC allergy; 2,341 who also had sulfonamide antibiotic allergy, as well as 52 new ACC allergies (0.87%) were reported.

CONCLUSIONS

The incidence of new ACC allergy reports is minimally and no-specifically increased when a preexisting ACC or sulfonamide antibiotic allergy exists greater than the baseline incidence in the population. This argues against clinically significant, immunologically mediated cross-reactivity among β-lactams sharing exact side chains in individuals with preexisting but unconfirmed β-lactam allergy. Any previously reported, even unrelated antibiotic allergy appears to be a risk factor for reporting a new antibiotic allergy.