Amoxicillin skin reactions with

A 40-year-old male nurse developed facial angioedema, dyspnea, rhinoconjunctivitis, dysphonia, and dysphagia immediately after opening a sachet containing amoxicillin and clavulanic acid (149). Skin prick tests were positive for both amoxicillin and ampicillin, and an open test with amoxicillin resulted in a severe immediate-type reaction with large localized wheals and erythema at 10 minutes. Six months later, when he was asymptomatic, erythema was observed during open tests with ampicillin 5%. 

In a retrospective review of 1068 patients with a self-reported history of beta-lactam allergy who had skin tests with penicilloyl— polylysine, penicillin G, penicilloate, penilloate, and amoxicillin, 243 (23%) had a positive reaction and testing with amoxicillin was positive in 31% of those 14 of the 243 positive patients (5.8%) had a positive skin tests only to amoxicillin [39 ]. 

The question of tolerability of penicillins, monobactams, and carbapenems in patients with IgE hypersensitivity to cephalosporins was recently assessed in 98 subjects by serum IgE antibody assays, challenge tests, and skin testing with penicillin reagents, aztreonam, imipenem-cilastatin, and meropenem. Approximately 25 % of cephalosporin-allergic subjects were positive to penicillins, while 3.1,2, and 1 % showed positive results to aztreonam, imipenem, and meropenem, respectively. A reaction to a cephalosporin with a similar or identical side chain to penicillin was a sigifificant predictor of cross-reactivity. For skin testing, the following concentrations were used ampicillin and amoxicillin 1 and 20 mg/ml cephalosporins 2 mg/ml aztreonam 2 mg/ml imipenem-cilastatin 0.5 mg/ml and meropenem 1 mg/ml. 

Skin The increased risk of a maculopapu-lar rash after the use of amoxicillin in patients with infectious mononucleosis has been illustrated by the case of a 24-year-old woman who developed such a rash after a single dose of amoxicillin 500 mg [89 ]. Reactivation of human herpesvirus 6 may also lead to skin reactions, as suggested by a series of seven cases of amoxicillin-induced flares in patients with drug reactions with eosinophilia and systemic symptoms (DRESS) due to other drugs in in vitro studies in a human T lymphoblas-toid MT4 cell line, amoxicillin increased replication of human herpesvirus 6 [90 ]. 

Clavulanic acid has a very low immunogenic and allergenic potential in animals. The possible impact of its co-administration with other beta-lactam antibiotics is unknown (53). Two patients with IgE-mediated hypersensitivity to oral co-amoxiclav and positive skin tests for clavulanic acid, but not for penicillins, both tolerated oral amoxicillin. One patient was also challenged with clavulanic acid and developed urticaria, conjunctivitis, and bronchial obstruction (54). Since co-amoxiclav has been widely used since its introduction in 1981, the frequency of hypersensitivity reactions is low. The clinical data available on sulbactam and tazobactam are stiU hm-ited and do not allow an assessment of the frequency and pattern of associated hypersensitivity reactions (55). 

Mechanisms of non-immediate reactions are unclear but may be immunological and non-immunological. Delayed reactions of the IgE type are known (131). Aminopenicillins seem to be an important cause of non-immediate reactions (132-134). The morbilliform rash that begins 1-10 days after amoxicillin can be caused by a delayed cell-mediated immune reaction (135) as can fixed drug eruptions (136,137), toxic epidermal necrolysis (138-140), bullous erythroderma (141), and contact eczema (142). Investigation of these disorders should include delayed readings of skin tests (135). In patients with chronic urticaria, penicillin allergy was demonstrated by cutaneous tests. 

Comment should be made on what sometimes seems like a preoccupation with employing penicillins in skin tests to predict aUergy to cephalosporins. Investigations have shown that <20 % of patients with immediate reactions to cephalosporins react to benzylpeniciUin, amoxicillin. 

In an evaluation of 276 patients who had a reaction attributed to amoxicUlin-clavulanic acid, 55 patients (19.9 %) reacted positively to different penicillin determinants. Of the 221 with negative skin tests, 15 were positive to amoxicillin and seven were judged to be allergic to clavulanic acid on the basis of tolerance to benzylpenicillin and amoxicillin and an immediate reaction to clavulanic acid following challenges. In the skin test-positive group, skin and... 

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