Cross-reactivity between penicillins and cephalosporins: clinical and immunologic studies

Drug Allergy Practice Parameter Updates to Incorporate Into Your Clinical Practice

The drug allergy practice parameter was developed to provide guidance on the diagnosis and management of drug hypersensitivity reactions. It was last updated in 2010. With the growth of research and evidence-based data since then, experts came together to update the practice parameter with a focus on sections that the work group deemed to have significant changes (or were not addressed) in the previous practice parameter. This review is a focused update on aspects of the practice parameter deemed to have the greatest impact on clinical practice and includes significant updates on diagnosis of antibiotic allergy including penicillin, cephalosporin, sulfonamide, fluoroquinolone, and macrolide allergies. Other topics include the evolution in our management approach to patients with aspirin/nonsteroidal anti-inflammatory drug allergy, diagnostic testing for delayed drug hypersensitivity and allergy to chemotherapeutics and biologics, and the key consensus-based statements for clinical practice. Specifically, the updated practice parameter helps allergists understand the place of 1- or 2-step drug challenges that are valuable tools often without the need for skin testing in many clinical situations. A proactive approach to delabeling penicillin allergy as well as unnecessary avoidance of safe antibiotic alternatives for patients with proven penicillin allergy is emphasized. New guidance is provided on management of patients with different phenotypes of aspirin and nonsteroidal anti-inflammatory drug hypersensitivity reactions. Approaches to delayed drug hypersensitivity and use of delayed intradermal and patch testing for specific phenotypes are reviewed. Lastly, practical approaches to management of patients with reactions to chemotherapeutics and biologics are discussed.

β-Lactam Allergy and Cross-Reactivity: A Clinician's Guide to Selecting an Alternative Antibiotic

β-Lactams which include penicillins, cephalosporins, carbapenems, and monobactams are the most common antibiotic classes reported to cause allergic reactions to drugs. This review is mainly about published studies assessing the cross-reactivity among β-lactams in penicillin- or cephalosporin-allergic subjects by carrying out diagnostic tests with alternative β-lactams and, if appropriate, graded challenges. Several studies demonstrated that cross-reactivity connected with the β-lactam ring, causing positive responses to allergy tests with all β-lactams, is infrequent in subjects with an IgE-mediated allergy and anecdotal in those with a T-cell-mediated allergy. Identities or similarities of β-lactam side-chain structures are mainly responsible for cross-reactivity among these antibiotics. For example, in aminopenicillin-allergic subjects, cross-reactivity with aminocephalosporins could possibly be over 30%. On the other hand, in a few prospective studies of penicillin-allergic individuals, less than 1% of cases show a cross-reactivity between penicillins and both aztreonam and carbapenems. Particular patterns of allergy-test positivity observed in some studies that assessed cross-reactivity among β-lactams seem to indicate that prior exposures may be responsible for coexisting sensitivities. Therefore, pre-treatment skin tests with the related β-lactams are suggested before administering them via graded challenges to β-lactam-allergic patients who need alternative β-lactams.

Immediate cephalosporin allergy

BACKGROUND

Patients who suffer from acute IgE-mediated allergy to a cephalosporin antibiotic are frequently assumed to be at high risk of allergy to other cephalosporins and penicillins.

AIM

To define cross-reactivity patterns in patients with confirmed allergy to a cephalosporin.

METHODS

Subjects presenting with a history of immediate allergy to a cephalosporin-family antibiotic between March 2009 and July 2017 were investigated with specific IgE testing to penicillin, amoxycillin and cefaclor, followed by skin prick testing, intradermal testing and drug provocation testing with a panel of penicillins and cephalosporins.

RESULTS

Out of 564 subjects with a reported beta-lactam allergy, 90 identified a cephalosporin as their index drug. Fifty-five (61.1%) of the 90 subjects tested had a history consistent with an IgE-mediated reaction, of whom 24 (43.6%) were proven to be allergic to their index cephalosporin. Twenty (83.3%) of the 24 were allergic only to their index cephalosporin. Of the four remaining subjects, two were co-sensitised to another beta-lactam with a similar side chain, while the other two had no specific cross-reactivity pattern. Major and minor penicillin determinants were negative for all cephalosporin-allergic individuals.

CONCLUSION

In our cohort, cephalosporin allergy does not appear to be a class effect, with most cases found allergic only to their index cephalosporin. Co-sensitisation to other cephalosporins or penicillins was uncommon, and when it occurred, was usually consistent with side chain cross-reactivity.

Tolerability of Cefazolin and Ceftibuten in Patients with IgE-Mediated Aminopenicillin Allergy

BACKGROUND

Side-chain similarities or identities constitute the predominant factor for cross-reactivity between penicillins and cephalosporins, whereas differences in the side-chain structure seem to account for the absence of such cross-reactivity.

OBJECTIVE

We sought to assess the cross-reactivity between penicillins and 2 cephalosporins (ie, cefazolin and ceftibuten) that have side chains different from those of penicillins, as well as to evaluate the possibility of using these cephalosporins in penicillin-allergic subjects.

METHODS

We conducted a prospective study of 131 consecutive subjects who had suffered 170 immediate reactions (mostly anaphylaxis) to penicillins and had positive skin test results to at least 1 penicillin reagent. All patients underwent skin tests with cefazolin and ceftibuten. Patients with negative results were challenged with them.

RESULTS

One participant had positive skin test results to cefazolin and ceftibuten, as well as to all other reagents tested, including aztreonam and carbapenems. All 129 subjects who underwent challenges with cefazolin and ceftibuten tolerated them. One subject refused cephalosporin challenges.

CONCLUSIONS

Subjects with an IgE-mediated hypersensitivity to penicillins could be treated with cephalosporins such as cefazolin and ceftibuten, which are among the cephalosporins that have side-chain determinants different from those of penicillins. Nevertheless, in patients with such hypersensitivity who need these alternative β-lactams, pretreatment skin tests are advisable because of the possibility of coexisting sensitivities or, much less frequently, of a sensitivity to an antigenic determinant of the common β-lactam ring.

The challenge of de-labeling penicillin allergy

BACKGROUND

Even though 8%-25% of most populations studied globally are labeled as penicillin allergic, most diagnoses of penicillin allergy are made in childhood and relate to events that are either not allergic in nature, are low risk for immediate hypersensitivity, or are a potential true allergy that has waned over time. Penicillin allergy labels directly impact antimicrobial stewardship by leading to use of less effective and broader spectrum antimicrobials and are associated with antimicrobial resistance. They may also delay appropriate antimicrobial therapy and lead to increased risk of specific adverse healthcare outcomes. Operationalizing penicillin allergy de-labeling into a new arm of antimicrobial stewardship programs (ASPs) has become an increasing global focus.

METHODS

We performed an evidence-based narrative review of the literature of penicillin allergy label carriage, the adverse effects of penicillin allergy labels, and current approaches and barriers to penicillin allergy de-labeling. Over the period 1928-2018 in Pubmed and Medline, search terms used included "penicillin allergy" or "penicillin hypersensitivity" alone or in combination with "adverse events," "testing," "evaluation," "effects," "label," "de-labeling," "prick or epicutaneous," and "intradermal" skin testing, "oral challenge or provocation," "cross-reactivity," and "antimicrobial stewardship".

RESULTS

Penicillin allergy labels are highly prevalent, largely inaccurate and their carriage may lead to unnecessary treatment and inferior outcomes with alternative agents as well as adverse public health outcomes such as antibiotic resistance.

CONCLUSIONS

Operationalizing penicillin allergy de-labeling as an aspect of ASP has become an increasing global focus. There is a need for validated approaches that optimally combine the use of history and ingestion challenge with or without proceeding formal skin testing to tackle penicillin allergy efficiently within complex healthcare systems. At the same time, there is great promise for penicillin allergy evaluation and de-labeling as an individual and public health strategy to reduce adverse healthcare outcomes, improve antimicrobial stewardship, and decrease healthcare costs.

Minor Determinants of Penicillin and Amoxicillin Are Still Key Components of Penicillin Skin Testing

BACKGROUND

The positive rate and pattern of penicillin skin test (PST) has been reported to be decreasing and changing. Previous studies differ about which penicillin component is the dominant component in positive PST result.

OBJECTIVE

To characterize past and current PST patterns to determine whether different determinants in PST have changed over time.

METHODS

A retrospective review of electronic medical records (January 2001-December 2017) was performed for patients who underwent PST. Data were divided into 4 cohorts to see whether trends occurred over time. The cohorts were divided as follows: cohort 1 (2001-2005), cohort 2 (2006-2010), cohort 3 (2011-2015), and cohort 4 (2016-2017).

RESULTS

A total of 30,883 patients underwent PST with the following breakdowns per cohort: cohort 1, 6,536; cohort 2, 10,372; cohort 3, 10,640; and cohort 4, 3,335. Of these, 329 patients (1.0%) had a positive PST result with a wheal of 3 × 3 mm or greater, with 110 in cohort 1, 130 in cohort 2, 67 in cohort 3, and 22 in cohort 4, whereas 170 patients (0.5%) had a positive PST result with a wheal of 5 × 5 mm or greater, with 54 in cohort 1, 72 in cohort 2, 34 in cohort 3, and 10 in cohort 4. When the positive PST rates of cohort 2 (1.25%), cohort 3 (0.6%), and cohort 4 (0.6%) were compared with those of cohort 1 (1.7%), there was a significant decrease in positive PST rates (P = .0278; P < .0001; P < .0001, respectively). When cohort 1 positive rate to benzylpenicillin polylysine among the positive PST (wheal of 3 × 3 mm or greater) was compared with those of the other cohorts (cohorts 2-4), the percent positive of benzylpenicillin polylysine in PST was 27% compared with 21% (P = .38), 34% (P = .5), and 18% (P = .6), respectively. When the positive PST result was defined as a wheal of 5 × 5 mm or greater, the positive rate for benzylpenicillin polylysine in PST increased over time (cohort 2: 22%, P = .8; cohort 3: 32%, P = .3; cohort 4: 40%, P = .264) compared with cohort 1 (19%).

CONCLUSIONS

Positive PST rate is decreasing. We demonstrate that despite benzylpenicillin polylysine solely positive rates remaining relatively stable, the minor penicillin determinants and amoxicillin play an important role in PST and their adoption into standard protocol for routine PST should be considered.

Cephalosporins: A Focus on Side Chains and β-Lactam Cross-Reactivity

Cephalosporins are among the most commonly prescribed antibiotic classes due to their wide clinical utility and general tolerability, with approximately 1-3% of the population reporting a cephalosporin allergy. However, clinicians may avoid the use of cephalosporins in patients with reported penicillin allergies despite the low potential for cross-reactivity. The misdiagnosis of β-lactam allergies and misunderstanding of cross-reactivity among β-lactams, including within the cephalosporin class, often leads to use of broader spectrum antibiotics with poor safety and efficacy profiles and represents a serious obstacle for antimicrobial stewardship. Risk factors for cephalosporin allergies are broad and include female sex, advanced age, and a history of another antibiotic or penicillin allergy; however, cephalosporins are readily tolerated even among individuals with true immediate-type allergies to penicillins. Cephalosporin cross-reactivity potential is related to the structural R1 side chain, and clinicians should be cognizant of R1 side chain similarities when prescribing alternate β-lactams in allergic individuals or when new cephalosporins are brought to market. Clinicians should consider the low likelihood of true cephalosporin allergy when clinically indicated. The purpose of this review is to provide an overview of the role of cephalosporins in clinical practice, and to highlight the incidence of, risk factors for, and cross-reactivity of cephalosporins with other antibiotics.

Cross-Reactivity to Cephalosporins and Carbapenems in Penicillin-Allergic Patients: Two Systematic Reviews and Meta-Analyses

BACKGROUND

There is no recent systematic review on the risk of cross-reactivity to cephalosporins and carbapenems in penicillin-allergic patients despite many new studies on the subject. All past reviews have several limitations such as not including any patient with a T-cell-mediated penicillin allergy.

OBJECTIVES

To determine the risk of cross-reactivity to cephalosporins and carbapenems in patients with a proven IgE- or T-cell-mediated penicillin allergy. To measure the association between R1 side chain similarity on cephalosporins and penicillins and the risk of cross-reactivity.

METHODS

MEDLINE and EMBASE were searched from January 1980 to March 2019. Studies had to include at least 10 penicillin-allergic subjects whose allergy had been confirmed by a positive skin test (ST) or drug provocation test (DPT) result. Cross-reactivity had to be assessed to at least 1 cephalosporin or carbapenem through ST or DPT. Both random-effects and fixed-effect models were used to combine data. A bioinformatic model was used to quantify the similarity between R1 side chains.

RESULTS

Twenty-one observational studies on cephalosporin cross-reactivity involving 1269 penicillin-allergic patients showed that the risk of cross-reactivity varied with the degree of similarity between R1 side chains: 16.45% (95% CI, 11.07-23.75) for aminocephalosporins, which share an identical side chain with a penicillin (similarity score = 1), 5.60% (95% CI, 3.46-8.95) for a few cephalosporins with an intermediate similarity score (range, 0.563-0.714), and 2.11% (95% CI, 0.98-4.46) for all those with low similarity scores (below 0.4), irrespective of cephalosporin generation. The higher risk associated with aminocephalosporins was observed whether penicillin allergy was IgE- or T-cell-mediated. Eleven observational studies on carbapenem cross-reactivity involving 1127 penicillin-allergic patients showed that the risk of cross-reactivity to any carbapenem was 0.87% (95% CI, 0.32-2.32).

CONCLUSIONS

Although it remains possible that these meta-analyses overestimated the risk of cross-reactivity, clinicians should consider the increased risk of cross-reactivity associated with aminocephalosporins, and to a lesser extent with intermediate-similarity-score cephalosporins, compared with the very low risk associated with low-similarity-score cephalosporins and all carbapenems when using beta-lactams in patients with a suspected or proven penicillin allergy.

Cephalosporin Allergy: Current Understanding and Future Challenges

Cephalosporins are commonly used antibiotics both in hospitalized patients and in outpatients. Hypersensitivity reactions to cephalosporins are becoming increasingly common with a wide range of immunopathologic mechanisms. Cephalosporins are one of the leading causes for perioperative anaphylaxis and severe cutaneous adverse reactions. Patients allergic to cephalosporins tend to tolerate cephalosporins with disparate R1 side chains but may react to other beta-lactams with common R1 side chains. Skin testing for cephalosporins has not been well validated but appears to have a good negative predictive value for cephalosporins with disparate R1 side chains. In vitro tests including basophil activation tests have lower sensitivity when compared with skin testing. Rapid drug desensitization procedures are safe and effective and have been used successfully for immediate and some nonimmediate cephalosporin reactions. Many gaps in knowledge still exist regarding cephalosporin hypersensitivity.

Cross-Reactivity and Tolerability of Cephalosporins in Patients with IgE-Mediated Hypersensitivity to Penicillins

BACKGROUND

Studies performed since 1990 on samples of at least 30 subjects with a documented IgE-mediated hypersensitivity to penicillins have found a rate of positive responses to allergy tests with cephalosporins ranging from 0% to 27%.

OBJECTIVE

We sought to assess the cross-reactivity with cephalosporins and evaluate the possibility of using cephalosporins in penicillin-allergic subjects.

METHODS

We conducted a prospective study of 252 consecutive subjects who had suffered 319 immediate reactions (mostly anaphylaxis) to penicillins and had positive skin tests to at least 1 penicillin reagent. All patients underwent serum specific IgE assays for cefaclor, as well as skin tests with 3 aminocephalosporins (cephalexin, cefaclor, and cefadroxil), cefamandole, cefuroxime, ceftazidime, ceftriaxone, cefotaxime, and cefepime. Patients with negative results for the last 5 cephalosporins were challenged with cefuroxime axetil and ceftriaxone; those with negative results for aminocephalosporins were also challenged with cefaclor and cefadroxil.

RESULTS

Ninety-nine participants (39.3%) had positive allergy tests for cephalosporins. Specifically, 95 (37.7%) were positive to aminocephalosporins and/or cefamandole, which share similar or identical side chains with penicillins. All 244 subjects who underwent challenges with cefuroxime axetil and ceftriaxone tolerated them. Of the 170 patients who underwent aminocephalosporin challenges, 3 reacted to cefaclor and 4 to cefadroxil.

CONCLUSIONS

Cross-reactivity between penicillins and cephalosporins seems to be mainly related to side chain similarity or identity. Subjects with an IgE-mediated hypersensitivity to penicillins could be treated with cephalosporins such as cefuroxime and ceftriaxone that have side-chain determinants different from those of penicillins and are negative in pretreatment skin testing.

Penicillin and Beta-Lactam Hypersensitivity

Ten percent of patients report penicillin allergy, but more than 90% of these individuals can tolerate penicillins. Skin testing remains the optimal method for evaluation of possible IgE-mediated penicillin allergy and is recommended by professional societies, as the harms for alternative antibiotics include antimicrobial resistance, prolonged hospitalizations, readmissions, and increased costs. Removal of penicillin allergy leads to decreased utilization of broad-spectrum antibiotics, such as fluoroquinolones and vancomycin. There is minimal allergic cross-reactivity between penicillins and cephalosporins. IgE-mediated allergy to cephalosporins is usually side-chain specific and may warrant graded challenge with cephalosporins containing dissimilar R1 or R2 group side chains.

Cross-Reactivity among Beta-Lactams

Penicillins and cephalosporins are the major classes of beta-lactam (BL) antibiotics in use today and one of the most frequent causes of hypersensitivity reactions to drugs. Monobactams, carbapenems, oxacephems, and beta-lactamase inhibitors constitute the four minor classes of BLs. This review takes into account mainly the prospective studies which evaluated cross-reactivity among BLs in subjects with a well-demonstrated hypersensitivity to a certain class of BLs by performing allergy tests with alternative BLs and, in case of negative results, administering them. In subjects with either IgE-mediated or T-cell-mediated hypersensitivity, cross-reactivity among BLs, particularly among penicillins and among cephalosporins, as well as between penicillins and cephalosporins, seems to be mainly related to structural similarities among their side-chain determinants. Specifically, in penicillin-allergic subjects, cross-reactivity between penicillins and cephalosporins may exceed 30% when they are administered cephalosporins with identical side chains to those of responsible penicillins. In these subjects, a few prospective studies have demonstrated a rate of cross-reactivity between penicillins and both carbapenems and aztreonam lower than 1%. With regard to subjects with an IgE-mediated hypersensitivity to cephalosporins, in a single study, about 25% of the 98 subjects with such hypersensitivity had positive results to penicillins, 3% to aztreonam, 2% to imipenem/cilastatin, and 1% to meropenem. The cross-reactivity related to the selective recognition of the BL ring by IgE or T lymphocytes, which entails positive responses to all BLs tested, appears to be exceptional. Some studies concerning cross-reactivity among BLs have found patterns of allergy-test positivity which cannot be explained by either the common BL ring or by similar or identical side chains, thus indicating the possibility of coexisting sensitivities to different BLs because of prior exposures to them.

Safe use of selected cephalosporins in penicillin-allergic patients: A meta-analysis

Background

Recent analysis of clinical data and a clearer understanding of the role of chemical structure in the development of cross-reactivity indicate that the increased risk of an allergic reaction to a cephalosporin in penicillin-allergic patients is smaller than previously postulated.

Method

Medline and EMBASE databases were searched with the keywords: cephalosporin, penicillin, allergy, and crosssensitivity for the years 1960 through 2005. Among 219 articles retrieved, 9 served as source material for this evidence-based meta-analysis.

Results

A significant increase in allergic reactions to cephalothin (odds ratio [OR] = 2.5; 95% confidence interval [CI] = 1.1 to 5.5), cephaloridine (OR = 8.7; CI = 5.9 to 12.8), and cephalexin (OR = 5.8; CI = 3.6 to 9.2), and all first generation cephalosporins plus cefamandole (OR = 4.8; CI = 3.7 to 6.2) were observed in penicillin allergic patients; no increase was observed with second generation cephalosporins (OR = 1.1; CI, 0.6 to 2.1) or third generation cephalosporins (OR = 0.5; CI = 0.2 to 1.1). Clinical challenges, skin testing, and monoclonal antibody studies point to the paramount importance of similarities in side chain structure to predict cross-allergy between cephalosporins and penicillins.

Conclusion

First-generation cephalosporins have cross-allergy with penicillins, but cross-allergy is negligible with second-and third-generation cephalosporins. Particular emphasis should be placed on the role of chemical structure in determining the risk of cross-reactivity between specific agents. 2007 American Academy of Otolaryngology-Head and Neck Surgery Foundation. All rights reserved.

Cross-reactivity and tolerability of aztreonam and cephalosporins in subjects with a T cell-mediated hypersensitivity to penicillins

BACKGROUND

The few studies performed in adults with T cell-mediated hypersensitivity to penicillins have found a rate of cross-reactivity with cephalosporins ranging from 2.8% to 31.2% and an absence of cross-reactivity with aztreonam.

OBJECTIVE

We sought to evaluate the possibility of using cephalosporins and aztreonam in subjects with documented delayed hypersensitivity to penicillins who especially require them.

METHODS

We conducted a prospective study of 214 consecutive subjects who had 307 nonimmediate reactions to penicillins (almost exclusively aminopenicillins) and had positive patch test and/or delayed-reading skin test responses to at least 1 penicillin reagent. To assess cross-reactivity with cephalosporins and aztreonam and the tolerability of such alternative β-lactams, all subjects underwent skin tests with cephalexin, cefaclor, cefadroxil, cefuroxime, ceftriaxone, and aztreonam. Subjects with negative responses were challenged with the alternative β-lactams concerned.

RESULTS

All subjects had negative skin test results to cefuroxime, ceftriaxone, and aztreonam and tolerated challenges. Forty (18.7%) of the 214 subjects had positive skin test responses to at least 1 aminocephalosporin. Of the 174 subjects with negative responses, 170 underwent challenges; 1 reacted to cefaclor.

CONCLUSIONS

These data demonstrate a rate of cross-reactivity between aminopenicillins and aminocephalosporins (ie, cephalexin, cefaclor, and cefadroxil) of around 20%, as well as the absence of cross-reactivity between penicillins and cefuroxime, ceftriaxone, and aztreonam in all subjects with T cell-mediated hypersensitivity to penicillins, almost exclusively aminopenicillins. Therefore these subjects could be treated with cefuroxime, ceftriaxone, and aztreonam. In those who especially require cephalosporin or aztreonam treatment, however, we recommend pretreatment skin tests because negative responses indicate tolerability.

Immunologic evaluation of immediate hypersensitivity to cefaclor

PURPOSE

Cefaclor is widely prescribed for various infectious diseases. As its consumption increases, the number of hypersensitivity reactions to cefaclor has increased. This study aimed to evaluate the immunologic findings of immediate hypersensitivity to cefaclor.

MATERIALS AND METHODS

We enrolled 47 patients with immediate hypersensitivity to cefaclor from Ajou University Hospital and Asan Medical Center. Serum specific IgE, IgG1, and IgG4 antibodies to cefaclor-human serum albumin (HSA) conjugate were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The most common phenotype was anaphylaxis (Group I, 78.7%), followed by urticaria (Group II, 21.3%). The detection of specific IgE, IgG1, and IgG4 to cefaclor-HSA conjugate by ELISA tended to be higher in Group I (40.5%, 41.7%, 21.6%) than in Group II (20.0%, 20.0%, 0%) with no statistical significance. Significant associations were found between specific IgE and IgG1 or IgG4 (p<0.001, p=0.019). ELISA inhibition tests showed significant inhibitions by both free cefaclor and cefaclor-HSA conjugate. For basophil activation tests in patients having no specific IgE antibody, the CD63 expression level on basophils increased with incubations of free cefaclor.

CONCLUSION

The most common manifestation of immediate hypersensitivity to cefaclor was anaphylaxis, most of which was mediated by IgE; however, a non-IgE mediated direct basophil activation mechanism was suggested in a subset of anaphylaxis patients.

Diagnosis and management of immediate hypersensitivity reactions to cephalosporins

Cephalosporins can cause a range of hypersensitivity reactions, including IgE-mediated, immediate reactions. Cephalosporin allergy has been reported with use of a specific cephalosporin, as a cross-reaction between different cephalosporins or as a cross-reaction to other β-lactam antibiotics. Unlike penicillins, the exact allergenic determinants of cephalosporins are less well understood and thus, standardized diagnostic skin testing is not available. Nevertheless, skin testing with diluted solutions of cephalosporins can be valuable in confirming IgE-mediated hypersensitivity reactions. In vitro tests are in development using recent technological advances and can be used as complementary tests. However, they are not commonly used because of their reduced sensitivity and limited availability. In selected cases of inconclusive results in both skin tests and IgE assays, a graded challenge or induction of drug tolerance with the implicated cephalosporin should be performed.

Beta-Lactam Hypersensitivity and Cross-Reactivity

Penicillin is the most frequently reported cause of drug allergy, and cross-reactivity of penicillins with other beta-lactam antibiotics is an area of debate. This review evaluates the available data on immunoglobulin E-mediated penicillin hypersensitivity and cross-reactivity with cephalosporin, carbapenem, and monobactam antibiotics. A MEDLINE search was conducted from 1950 to October 2013, and selected references from review articles were also evaluated. There is a wide variety in reported incidences of cross-reactivity between penicillins and cephalosporins or carbapenems, with early retrospective studies suggesting up to 41.7% and 47.4% cross-reactivity, respectively. Conversely, the use of monobactam antibiotics is frequently employed in the case of a penicillin allergy, as prescribers believe that there is no cross-reactivity between the 2 drug classes. More recent prospective studies suggest that the rates of cross-reactivity with cephalosporins and carbapenems are <5% and <1%, respectively. Similarities in penicillin and cephalosporin side chains may play a role in cross-reactivity between these classes. Cross-reactivity with monobactams is essentially negligible; however, there are some clinical data to support an interaction between ceftazidime and aztreonam, due to the similarity of their side chains. The data reviewed suggest that avoidance of other beta-lactams in patients with type 1 hypersensitivity to penicillins should be reconsidered.

Review of the use of cephalosporins in children with anaphylactic reactions from penicillins

OBJECTIVE

It is a widely accepted practice that children with anaphylaxis from penicillins should avoid cephalosporins. The purpose of the present study was to determine whether there is evidence in the literature to support this practice.

DATA SOURCES

MEDLINE, EMBASE, Toxline, International Pharmaceutical Abstracts and PubMed were used to search the literature published from 1966 to 2001. The Canadian Medical Protective Association, Health Canada and the Boston Collaborative Drug Surveillance Program were also contacted to determine whether there were any unpublished cases of cross-reactivity between penicillins and cephalosporins.

DATA EXTRACTION

Cases describing the use of cephalosporins in adults and children with positive penicillin skin tests or anaphylaxis from penicillin were evaluated. Case reports of anaphylaxis from cephalosporins in paediatric patients were identified.

DATA SYNTHESIS

There have been five reported cases of serious reactions from cephalosporins in patients with a history of anaphylaxis from penicillins. All cases occurred in adults; three developed anaphylaxis from the older, first-generation cephalosporins, cephalothin and cephaloridine; one developed anaphylaxis from cefamandole; and one developed anaphylaxis from cefaclor. There have been 12 other published reports of anaphylaxis from cephalosporins in adults with a history of penicillin allergy or a positive penicillin skin test, but with no history of anaphylaxis from penicillin. In seven studies, in which a total of 158 patients with positive penicillin skin tests were administered cephalosporins, seven had apparent immunoglobulin E-mediated reactions when they were given a cephalosporin. When the class of cephalosporin was able to be determined, none of the reports of reactions from cephalosporins in patients with allergies to penicillin involved third-generation cephalosporins. There have been 13 case reports of anaphylaxis from cephalosporins in paediatric patients.

CONCLUSION

There are no published case reports of anaphylaxis from cephalosporins in children with anaphylaxis from penicillin, and there are only a small number of such reports in adults. Anaphylaxis from cephalosporins appears to be incredibly rare in children. There is minimal evidence in the literature to support the avoidance of cephalosporins in children with anaphylaxis from penicillins.

The use of cephalosporins in penicillin-allergic patients: a literature review

BACKGROUND

The practice of avoiding cephalosporin administration to penicillin-allergic patients persists despite the low rate of cross reactions between both groups of antibiotics.

OBJECTIVE

The purpose of this literature review is to evaluate the published evidence regarding the commonly held belief that patients with a history of an allergic reaction to penicillin have a significantly increased risk of an allergic reaction to cephalosporins.

MATERIALS AND METHODS

Articles were identified through a computerized search of MEDLINE from 1950 to the present using the search terms "penicillin$," "cephalosporin$," "allerg$," "hypersensitivity," and "cross-react$." All articles were reviewed, and additional sources cited in them were added to the literature review.

RESULTS

Penicillins have a cross allergy with first-generation cephalosporins (odds ratio 4.8; confidence interval 3.7-6.2) and a negligible cross allergy with second-generation cephalosporins (odds ratio 1.1; confidence interval 0.6-2.1). Laboratory and cohort studies confirm that the R1 side chain is responsible for this cross reactivity. Overall cross reactivity between penicillins and cephalosporins is lower than previously reported, though there is a strong association between amoxicillin and ampicillin with first- and second-generation cephalosporins that share a similar R1 side chain.

CONCLUSIONS

Although a myth persists that approximately 10% of patients with a history of penicillin allergy will have an allergic reaction if given a cephalosporin, the overall cross-reactivity rate is approximately 1% when using first-generation cephalosporins or cephalosporins with similar R1 side chains. However, a single study reported the prevalence of cross reactivity with cefadroxil as high as 27%. For penicillin-allergic patients, the use of third- or fourth-generation cephalosporins or cephalosporins with dissimilar side chains than the offending penicillin carries a negligible risk of cross allergy.

Use of selected cephalosporins in penicillin-allergic patients: a paradigm shift

Recent analysis of clinical data and a clearer understanding of the role of chemical structure in the development of cross-reactivity indicate that the increased risk of an allergic reaction to certain cephalosporins in penicillin-allergic patients is smaller than previously postulated. Medline and EMBASE databases were searched using the following keywords: cephalosporin, penicillin, allergy, and cross-sensitivity for the years 1960 to 2005. Among 219 articles retrieved, 106 served as source material for this review. A significant increase in allergic reactions to cephalothin, cephaloridine, cephalexin, cefazolin, and cefamandole was observed in penicillin-allergic patients; no increase was observed with cefprozil, cefuroxime, ceftazidime, or ceftriaxone. Clinical challenges, skin testing, and monoclonal antibody studies point to the paramount importance of similarities in side chain structure to predict cross-allergy between cephalosporins and penicillins. First-generation cephalosporins have a modest cross-allergy with penicillins, but cross-allergy is negligible with 2nd- and 3rd-generation cephalosporins. Particular emphasis is placed on the role of chemical structure in determining the risk of cross-reactivity between specific agents.

Safety and effectiveness of a preoperative allergy clinic in decreasing vancomycin use in patients with a history of penicillin allergy

BACKGROUND

We developed a clinical pathway to optimize the use of antimicrobials by decreasing vancomycin use in preoperative patients with a history of penicillin allergy.

OBJECTIVE

To decrease the use of vancomycin in surgical patients with a self-reported penicillin allergy.

METHODS

In June 2002, same-day allergy consultation and penicillin skin testing were made available for preoperative patients with self-reported penicillin allergy at the preoperative evaluation (POE) clinic. We reviewed the penicillin allergy skin test results, recommendations, and beta-lactam antibiotic administration outcomes from July 1, 2002, to September 16, 2003.

RESULTS

A total of 1,204 of 11,819 patients were evaluated for beta-lactam allergy at the POE clinic. Of these, 1,120 were approved by the institutional review board for inclusion in the study and 9 were excluded from the study. Of the remaining 1,111 patients, 1,030 (93%) underwent skin testing for penicillin allergy. Forty-three (4%) had a positive skin test result to penicillin. A total of 947 (85%) of the 1,111 patients with a history of beta-lactam allergy were advised to use a beta-lactam antibiotic, and 164 (15%) were advised to avoid beta-lactams. A total of 955 patients (86%) actually received preoperative antibiotics. Of these 955 patients, 716 (75%) received cefazolin, and only 149 (16%) received vancomycin compared with 30% historical controls (P < .01). Among the patients with a negative penicillin skin test result who received a cephalosporin, 5 (0.7%) of 675 experienced an adverse drug reaction to a cephalosporin.

CONCLUSIONS

Establishment of a clinical pathway in a preoperative clinic that includes allergy consultation and penicillin skin testing reduced vancomycin use to only 16% in surgical patients with a history of beta-lactam allergy.

Anaphylactic and anaphylactoid causes of angioedema

Anaphylactic and anaphylactoid (pseudoallergic) reactions can be expected to occur with greater frequency as the number of immunomodulators are employed. The immune system will become sensitized to these new therapeutic agents or there may be first-dose reactions depending on the pathogenetic mechanism involved. Physicians should review their office or procedure room emergency preparedness protocols and medications. The lack of penicillin major and minor determinants for penicillin testing has made management of penicillin and cephalosporin allergic patients more complicated. In the absence of skin-testing materials, test-challenges will be necessary and performed with less comfort because of not knowing the current level of immunologic sensitization to penicillin. The indication for readministration of any incriminated medication/therapeutic agent should be reviewed. Often, there are not suitable alternatives. Various approaches have been presented to permit safer readministration of essential medications or diagnostic agents to prevent episodes of anaphylaxis or upper airway angioedema.

Antibiotic selection in the penicillin-allergic patient

Clinicians should be familiar with which antibiotics are safe to use for different types of penicillin-allergic reactions. Clinically, it is convenient to divide patients with penicillin allergy into three categories: those with unknown or possible reactions to penicillin, those with a drug fever or rash, and those with hives or anaphylactic reactions. Beta-lactam antibiotics may be used safely for patients with unknown/possible penicillin allergy and drug fever or rash. Penicillins or beta-lactams should not be used for patients with hives or anaphylactic reactions. For all patients, clinicians should consider antimicrobial therapy with an antibiotic that does not cross-react with penicillins or beta-lactams. This article reviews how clinicians should select antimicrobials in penicillin-allergic patients.

Immediate allergic reactions to cephalosporins: evaluation of cross-reactivity with a panel of penicillins and cephalosporins

BACKGROUND

Allergy to cephalosporins has mainly been evaluated in the context of patients with confirmed penicillin allergy. The problem of studying cross-reactivity in subjects primarily sensitized to cephalosporins and potentially allergic to penicillins has not been sufficiently addressed.

OBJECTIVE

To evaluate the in vitro IgE response and cross-reactivity to betalactams in patients with immediate allergic reactions to cephalosporins.

METHODS

The study included 24 patients with immediate allergic reactions to cephalosporins and RAST-positive to at least 1 cephalosporin. Skin testing and RAST were performed with a panel of penicillins and cephalosporins. RAST inhibition assay with different monomeric conjugates of penicillin and cephalosporin was performed to establish cross-reactivity.

RESULTS

The culprit cephalosporins were cefaclor (N = 7), cefonicid (N = 1), cefotaxime (N = 2), ceftazidime (N = 2), ceftriaxone (N = 3), and cefuroxime (N = 9). Two patients had a positive skin test result to penicillin determinants, and 22 patients had a negative result to penicillin determinants and tolerated benzylpenicillin administration. Of these 22, 19 had a positive skin test result to cephalosporins and divided into patients reacting only to the culprit cephalosporin (63.2%) and those reacting to more than 1 cephalosporin (36.8%). RAST and RAST inhibition studies confirmed that the side chain at the R1 position is crucial for recognition.

CONCLUSION

The R1 side chain rather than the betalactam structure, shared by penicillins and cephalosporins, seems to play a dominant role in determining the specificity of immunologic reactions to cephalosporins. Thus, penicillin can be administered safely to patients allergic to cephalosporins and with a negative skin test result to penicillin determinants.

Antibiotic allergy in cystic fibrosis

Allergic reactions to antibiotics are more common in cystic fibrosis (CF) than in the general population. This in part is due to the improving survival in adults with CF and the increased use of high dose intravenous antibiotics. While some are immediate anaphylaxis type (IgE mediated) reactions, the majority are late onset and may have non-specific features such as rash and fever. Piperacillin has consistently been found to have the highest rate of reported reactions (30-50%). There is a low risk of cross reactions between penicillins and other non-beta-lactam classes of antibiotics in penicillin skin prick positive patients. Carbapenems should only be used with extreme caution in patients with positive skin prick tests to penicillin. However, aztreonam can be used safely in patients who are penicillin allergic with positive skin prick reactions. The aminoglycosides are a relatively uncommon cause of allergic reactions, but patients who react to one member of the family may cross react with other aminoglycosides. Desensitisation relies on the incremental introduction of small quantities of the allergen and has been used for penicillins, ceftazidime, tobramycin and ciprofloxacin and must be repeated before each course. Personalized cards should be regularly updated for patients who develop allergic reactions. Written instructions on the emergency treatment of allergic reactions should be provided to patients self-administering intravenous antibiotics at home. Further research is required to identify risk factors and predictors for antibiotic allergy.

Cross-reactivity among drugs: clinical problems

Cross-reactivity among drugs is either mediated by immunologic mechanisms or not. The former kind is usually explained by the presence of common antigenic determinants in the cross-reacting drugs. In the case of compounds provoking non-allergic hypersensitivity reactions, cross-reactivity is explained by a common pharmacological characteristic, such as the inhibitory effect of non-steroidal anti-inflammatory drugs on cyclooxygenase-1 and the capability of muscle relaxants or contrast media to release histamine through a non-immunologic mechanism. The main clinical problem deriving from cross-reactivity among drugs is the compelling need to choose a potentially cross-reactive compound and, therefore, to assess cross-reactivity by diagnostic tests. In choosing alternative compounds, skin testing has been used in evaluating IgE-mediated cross-reactivity between penicillins and cephalosporins, as well as among muscle relaxants. In assessing T cell-mediated cross-reactivity among contrast media, corticosteroids, anticonvulsants and heparins, delayed-reading intradermal tests and patch tests, together with lymphocyte transformation tests, can be performed. Because of the limited sensitivity of in vivo and in vitro testing, the most prudent way of establishing the tolerability of a compound of the same group in patients who especially require one is a graded challenge when other allergologic tests are negative.

A review of evidence supporting the American Academy of Pediatrics recommendation for prescribing cephalosporin antibiotics for penicillin-allergic patients

The American Academy of Pediatrics, evidence-based guidelines endorse the use of cephalosporin antibiotics for patients with reported allergies to penicillin, for the treatment of acute bacterial sinusitis and acute otitis media. Many physicians, however, remain reluctant to prescribe such agents. Although such concern is understandable, lack of consistent data regarding exactly what constitutes an initial penicillin-allergic reaction and subsequent cross-sensitivity to cephalosporins may be preventing many patients from receiving optimal antibiotic therapy. This article reviews evidence in support of the American Academy of Pediatrics recommendation. Included is an examination of the types and incidence of reactions to penicillins and cephalosporins; the frequency of cross-reactivity between these 2 groups of agents; experimental and clinical studies that suggest that side chain-specific antibodies predominate in the immune response to cephalosporins, thereby explaining the lack of cross-sensitivity between most cephalosporins and penicillins; the role of skin testing; and the risks of anaphylaxis. Specific recommendations for the treatment of patients on the basis of their responses to previously prescribed agents are summarized.

Diagnosis and management of penicillin allergy

Among patients with a reported history of penicillin allergy, 80% to 90% have no evidence of IgE antibodies to penicillin on skin testing and thus avoid penicillin unnecessarily. Moreover, 97% to 99% of such patients with a penicillin skin test negative to the major and minor determinants can tolerate penicillin without risk of an immediate-type hypersensitivity reaction. A penicillin skin test is valuable for evaluating penicillin allergy in patients who need penicillin or cephalosporin. Assessment of sensitivities to penicillin is important to reduce the unnecessary use of antimicrobial agents such as vancomycin. We review the role of penicillin skin testing for evaluating penicillin allergy and the use of cephalosporin in patients with a history of penicillin allergy.

Dilemmas and controversies in penicillin allergy

Since the initial reports of penicillin and beta-lactam drugs causing allergic reactions, much has been elucidated regarding their pathophysiology and mechanism of action. Despite advances in testing for penicillin allergy, with IgE antibodies and skin tests available for the major and minor determinants of penicillin, these reactions remain a challenge to all physicians. They have characteristically been classified according to mechanism and time. Herein, the authors propose a classification system of penicillin allergy based on immunologic mechanisms.

Immediate allergic reactions to betalactams: facts and controversies

PURPOSE OF REVIEW

To analyse the available data in the field of immediate allergic reactions to beta-lactams, with particular emphasis on more recent studies, and to comment on the future role of this group of antibiotics.

RECENT FINDINGS

The world of beta-lactams has become more complex than initially thought, due to the increased number of chemical structures available, the wide variety of indications for their use in treating different infectious diseases, and possibly also due to the interaction of other as yet undetermined factors. Benzyl penicillin, the original inducer of allergic reactions, has now largely been replaced by amoxicillin and, to a lesser extent, by cephalosporins in inducing IgE-mediated allergic reactions. These structures often share extensive cross-reactivity, eliciting clinical reactions to many compounds, especially amongst penicillins. In other circumstances selective responses are observed which are restricted to one group or one single compound, as occurs in the group of cephalosporins. The application of new determinants for skin testing and the use of adapted in-vitro studies have enabled these findings to be confirmed in detail.

SUMMARY

Results indicate that evaluation of immediate reactions to beta-lactams requires the use of several determinants for both in-vitro and in-vivo testing, and which must reflect the relevant drug involved in eliciting the response. This tendency will be strengthened in the future if use of benzyl penicillin continues to decrease as a drug to which populations are exposed.

Cephalosporin allergy

Allergic reactions to cephalosporins may occur because of sensitization to cephalosporin determinants shared with penicillin or to unique cephalosporin haptens. The exact nature of the haptenic determinants resulting from the degradation of currently available cephalosporins is incompletely understood. Cephalosporin skin testing or specific IgE immunoassays have limited clinical utility. Patients with a history of allergy to cephalosporins or penicillin may be at increased risk for a reaction to cephalosporins. Skin testing for an allergy to penicillin may be helpful in patients with a history of penicillin allergy who have a clinical indication for cephalosporin use. Most of these patients have negative tests and should not be at increased risk for a reaction to cephalosporins.