Amoxicillin and ear infection

Circulating beta-lactam-specific IgE antibodies can decrease naturally over time [7] .

However, many patients are never reassessed and continue to carry this label.

Beta-lactam antibiotics (penicillins and cephalosporins) share a beta-lactam ring.

Medications differ based on the different cetirizine and amoxicillin R groups on the acyl side chain (Figure 1).

Beta-lactam antibiotics develop allergenic potential when the beta-lactam ring opens and links with nearby proteins in the blood. Penicillins, slide 13: www.slideshare.net/seetaram443/penicillins-53561419. Cross-reactivity among beta-lactam antibiotics in allergic individuals. Cross-reactivity among the penicillins is caused primarily by similarities in their core ring structure and their side chains. Cross-reactivity cannot be determined by side-chain similarities alone.

When a patient has a true allergy to a penicillin, all penicillins should be avoided. It was previously believed that cephalosporin allergy occurred in 10% to 20% of penicillin-allergic individuals, and that they should avoid all cephalosporins.

However, it is now understood that this occurrence rate was an overestimation, and that associated precautions were overly restrictive. Although these medications share a common beta-lactam ring (Figure 2), evidence has shown that it is rarely the structure implicated in allergy [2] . All early cases reported were in patients who received first-generation medications. Pre-1980 cephalosporins were found to be contaminated with penicillin, and these early reactions are now known to

have

For example, when an individual has a confirmed allergy to amoxicillin, they are likely to react to cephalexin as well because of the group 2 side chain at position 7.

The true rate of cross-reactivity is thought to be about 2% [2] .

With the true incidence of penicillin allergy among patients who report a history

being

Chemical structures of 3-position side chains of cephalosporins Similar side-chain cross-reactivity within group Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 cefadroxil cephalexin cephradine cefmetazole cefoperazone cefotetan cefamandole cefotaxime cephalothin cephapirin ceftibuten ceftizoxime cefuroxime cefoxitin cefdinir cefixime Adapted from reference 8.

Detailed history-taking is critical to the evaluation of possible beta-lactam allergy, the level of patient risk, and for deciding whether skin testing or an oral challenge is indicated.

Individuals should be assessed and examined by a

physician

suspected

Thus, skin testing is less likely to be useful in children than in adults. Skin testing is not a useful test for screening of allergy where there is no history of a convincing reaction because the positive predictive value for penicillin allergy has been reported to be as low as 40% [2] . The gold standard test to rule out an IgE-mediated allergy is a drug challenge test, conducted when, after thorough history taking +/- skin testing, an individual is deemed unlikely to be allergic.

Skin testing with standardized reagents is specific to penicillin and does not necessarily rule out allergy to other penicillin group members with different side chains (e.g., amoxicillin).

Thus, oral drug challenge to the specific medication is preferred.

There is no international consensus on how challenge tests are to be conducted.

Many Canadian centres provide a single dose

challenge

Drug challenge tests in appropriately selected individuals are safe and effective, and recent data have indicated that going directly to oral challenge, without skin testing, is more reliable [5] . Drug challenge tests can be dangerous and are contraindicated if when a child’s history is consistent with recent anaphylaxis or systemic, non-immediate immunologic reaction (e.g., serum sickness-like reaction, SJS, DRESS syndrome, or drug-induced hemolytic anemia).

Clinical implications of erroneous beta-lactam allergy labelling. A diagnosis of drug allergy in children should be made with special care because inaccurate penicillin allergy labelling is associated with negative clinical and administrative outcomes.

Second-line non-beta-lactam antimicrobials are generally inferior for infection management and have been associated with prolonging hospital stays, higher admission rates for intensive care, readmissions, and mortality. As a result of increased alternative, broad-spectrum antibiotic use, antibiotic resistance is expanding and now includes vancomycin-resistant enterococcus and methicillin-resistant S. Rising health care costs around the world are due in part to higher antibiotic costs per hospitalization and prolonged hospital stays.

Removal of erroneous penicillin allergy labels has been shown to mitigate both trends [10] . Penicillin allergy

de-labelling