Delayed Allergy to Aminopenicillins: Clinical and Immunological Findings

Diagnosis and selection of alternative antibiotics in beta-lactams hypersensitivity reactions: Current recommendations and challenges

Beta-lactam (BLM) antibiotics, including amino-penicillin and cephalosporins, are typically the first-choice treatment for bacterial infections. However, adverse reactions to these antibiotics are frequently reported, causing non-allergist physicians to select alternative broad-spectrum antibiotics that can have harmful consequences. Patients with unclear histories of hypersensitivity reactions to BLMs should undergo an allergy workup to establish a firm diagnosis, particularly when different drugs are prescribed simultaneously. However, finding the safest, most precise, and cost-effective methods for confirming BLMs hypersensitivity and selecting the most appropriate alternative BLM is uncertain, particularly in severe delayed reactions. This review aims to provide data and recommendations on the availability and validity of skin tests (STs), drug provocation test (DPT) protocols, based on the latest published literature and guideline. To make the process more practical, we focused on cross-reactivity between BLMs and diagnostic tests. There are two main novel aspects of this document: 1) For T-cell-mediated reactions, patient stratification into high, moderate, and low-risk groups based on the mortality and morbidity of adverse drug reactions. 2) For IgE-mediated reactions, stratification of individuals with isolated limited urticarial without anaphylaxis in a low-risk group and removal of the extensive limitation.

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.

The Limited Value of Prolonged Drug Challenges in Nonimmediate Amoxicillin (Clavulanic Acid) Hypersensitivity

BACKGROUND

Misdiagnosis of amoxicillin (clavulanic acid) (AX(/CL)) hypersensitivity has serious consequences. A drug challenge (DC) is the final diagnostic to affirm or infirm AX(/CL) hypersensitivity. However, uncertainties remain whether a prolonged drug challenge (pDC) should benefit the diagnosis of a nonimmediate AX(/CL) hypersensitivity.

OBJECTIVE

To assess the added value of a standardized 7-day pDC in the diagnosis of nonimmediate or unclear penicillin hypersensitivity.

METHODS

A total of 132 patients with a history of a nonimmediate hypersensitivity reaction or an unclear reaction to AX(/CL) or an undefined penicillin with a negative diagnostic workup including a single-day DC (DC) with AX(/CL) were selected. In all these patients, an additional pDC with AX(/CL) was planned. Thirteen patients started the pDC immediately after the DC. To ensure that hypersensitivity symptoms manifesting during the pDC course do not result from the DC, in the remaining 119 patients, the pDC was scheduled after a washout of 1 week.

RESULTS

A total of 128 patients (12 without washout, 116 with washout) completed the pDC. Three patients reacted with a mild maculopapular exanthema. However, the value of a pDC was evidenced in only 1 patient who reacted during her pDC after an uneventful washout. In 2 patients pDC was cancelled because they reacted during the washout.

CONCLUSIONS

A pDC is of limited added value to the diagnostic algorithms of nonimmediate hypersensitivity reaction or unclear hypersensitivity reactions to AX(/CL). In our hands, the traditionally recommended diagnostic algorithm that offers a 1-day DC as a final diagnostic in patients with negative workup for AX(/CL) is appropriate.

Association of non-immediate drug hypersensitivity with drug exposure: A case control analysis of spontaneous reports from a Tunisian pharmacovigilance database

PURPOSE

To assess delayed-type cutaneous reactions (DTCRs) related to drugs, using a case-control approach to qualify drug risks.

METHODS

The study used the Tunisian pharmacovigilance database of Monastir. The association between drugs and DTCRs was assessed using a case/non-case method. Drugs were grouped according to the ATC Classification System. Patients were defined as "cases" if they have developed DTCRs regardless of the causality assessment. All other reports were "non-cases". Association between reactions and drugs was calculated using the reporting odds ratio (ROR) with 95% confidence intervals (CIs). A p value < 0.05 was considered significant.

RESULTS

The analysis was carried out on 1798 reports, of which 867 concerned DTCRs (cases) and 931 concerned non-cases. The calculated risk estimates were significant for cefotaxime (ROR 2.1; 95% CI 1.5 to 3), pristinamycin (ROR 4; 95% CI 2 to 7.9), sulfamethoxazole (ROR 4.4; 95% CI 1.6 to 11.7), oxacillin (ROR 2.2; 95% CI 1.2 to 3.8), doxycycline (ROR 10.8; 95% CI 1.4 to 84.9), carbamazepine (ROR 3.3; 95% CI 1.7 to 6.2), phenobarbital (ROR 2.3; 95% CI 1.03 to 5.1), allopurinol (ROR 3.6; 95% CI 1.8 to 7.2), furosemide (ROR 2.4; 95% CI 1.3 to 6.3), hydrochlorothiazide(ROR 2.9; 95% CI 1.3 to 6.3) and candesartan (ROR 4.7; 95% CI 1.3 to 16.6).

CONCLUSION

Our findings corroborate risks for a number of drugs, such as antibacterials, antiepileptics and allopurinol in inducing DTCRs. Given the widespread use of these drug classes, awareness should be raised among patients and prescribers about these risks.

Efficacy and Safety of 5-Day Challenge for the Evaluation of Nonsevere Amoxicillin Allergy in Children

BACKGROUND

Penicillin allergy is the most frequent drug allergy, among which aminopenicillins are reputed for causing delayed rashes in children, particularly in the context of viral infections. Despite a negative allergy evaluation, a significant proportion of individuals continue to avoid penicillin antibiotics for fear of an allergic reaction.

OBJECTIVE

To evaluate the safety and efficacy of a 5-day challenge to amoxicillin and the proportion of subsequent use of amoxicillin.

METHODS

Pediatric patients with a history of a reaction to amoxicillin were prospectively recruited in the study. All patients were challenged, and those with negative immediate challenges underwent an ambulatory 5-day challenge to amoxicillin to rule out nonimmediate reactions. Patients were called 2 years after their initial allergy evaluation to assess subsequent amoxicillin use and tolerance.

RESULTS

One hundred thirty children with a history of amoxicillin allergy underwent a graded drug provocation test (DPT) to amoxicillin. Three patients had a positive immediate challenge, 3 had a positive nonimmediate challenge, and 2 were equivocal. Of the 122 patients with a negative challenge, 114 (93.4%) were reached 2 years after their initial allergy evaluation: 75 had used antibiotics since, of which only 1 (1.3%) had refused to reuse amoxicillin because of fear of an allergic reaction. Finally, the 5-day DPT resulted in a 24.1% decrease in future penicillin avoidance compared with classical single-dose graded DPT performed for 1 day in a historical cohort (P < .0001).

CONCLUSION

The 5-day challenge is a safe and effective way to rule out nonimmediate amoxicillin allergy, and it ensures better compliance with future penicillin use.

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.

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.

Management of allergy to penicillins and other beta-lactams

The Standards of Care Committee of the British Society for Allergy and Clinical Immunology (BSACI) and an expert panel have prepared this guidance for the management of immediate and non-immediate allergic reactions to penicillins and other beta-lactams. The guideline is intended for UK specialists in both adult and paediatric allergy and for other clinicians practising allergy in secondary and tertiary care. The recommendations are evidence based, but where evidence is lacking, the panel reached consensus. During the development of the guideline, all BSACI members were consulted using a Web-based process and all comments carefully considered. Included in the guideline are epidemiology of allergic reactions to beta-lactams, molecular structure, formulations available in the UK and a description of known beta-lactam antigenic determinants. Sections on the value and limitations of clinical history, skin testing and laboratory investigations for both penicillins and cephalosporins are included. Cross-reactivity between penicillins and cephalosporins is discussed in detail. Recommendations on oral provocation and desensitization procedures have been made. Guidance for beta-lactam allergy in children is given in a separate section. An algorithm to help the clinician in the diagnosis of patients with a history of penicillin allergy has also been included.

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.

Cross-reactivity and tolerability of imipenem in patients with delayed-type, cell-mediated hypersensitivity to beta-lactams

BACKGROUND

Administration of imipenem-cilastatin to patients with IgE-mediated hypersensitivity to beta-lactams has always been considered potentially harmful. Recent studies have demonstrated the tolerability of carbapenems (imipenem-cilastatin and meropenem) in patients with IgE-mediated hypersensitivity to beta-lactams; there are no studies on this topic regarding patients with cell-mediated allergy to beta-lactams. The aim of this study is to assess cross-reactivity and tolerability of imipenem in patients with cell-mediated allergy to beta-lactams.

METHODS

From our database we selected 73 patients with cell-mediated allergy to beta-lactams, diagnosed by means of immediate-type skin tests, delayed reading intradermal tests, patch tests and detection of specific IgE. Patients with negative patch tests with imipenem-cilastatin underwent an intramuscular test dosing.

RESULTS

Our patients had a total of 94 nonimmediate reactions to penicillins. All patients had positive patch tests and/or delayed reading intradermal tests for at least one of the penicillin reagent tested and negative immediate-type skin tests and specific IgE. Four patients out of 73 had a positive patch tests to at least one penicillin reagent and imipenem-cilastatin showing cross-reactivity. Sixty-four patients underwent the imipenem-cilastatin intramuscular test dosing and none of them had a clinical reaction.

CONCLUSIONS

Our rate of cross-reactivity between imipenem-cilastatin and other beta-lactams was 5.5%. This result is different from previous findings and this may be explained by the fact that we investigated patients with cell-mediated allergy to beta-lactams. Patients with cell-mediated allergy to beta-lactams should undergo patch tests and a tolerance challenge test before treatment with imipenem-cilastatin.

Tolerability of Aztreonam in Patients with IgE-Mediated Hypersensitivity to Beta-Lactams

Cross-reactivity between aztreonam and penicillins is poor, but clinical tolerance of aztreonam has been assessed, by means of tolerance challenge tests, only in a few groups of penicillin-allergic patients. The aim of this study is to evaluate the tolerability of aztreonam in a large group of betalactam-allergic patients. We studied all patients (> 14 years of age), with a clinical history of immediate reactions to any betalactam and with positive immediate-type skin tests and/or positive specific IgE to any of the studied betalactam; they were studied by means of: skin prick and intradermal tests with penicilloyl polysine, minor determinant mixture, semisynthetic penicillins, cephalosporins, aztreonam and imipenem; detection of specific IgE to penicillin G, penicillin V, ampicillin, amoxicillin, cefaclor and ceftriaxone. Patients with negative immediate-type skin tests with aztreonam then underwent a graded intramuscular challenge. Forty-five patients (mean age 46.1 ± 15.2 years), 27 females and 18 males, had positive skin tests and/or specific IgE to at least one of the studied betalactams. The most involved drugs were amoxicillin (23 cases), ampicillin (9 cases), penicillin G (8 cases) and other betalactams in the remaining cases. The most frequent reactions were anaphylaxis (27 cases) and urticaria (15 cases). All patients had negative intradermal tests with aztreonam and all patients tolerated the intramuscular graded challenge. Our data confirm the lack of cross-reactivity between betalactams and aztreonam. Immediate-type skin tests with aztreonam represent a simple and rapid diagnostic tool to establish tolerability in betalactam-allergic patients who urgently need this drug.