Skin Testing with Cephalosporins

76 patients with histories of immediate reactions to cephalosporins. Individual cephalosporins tested were cephalothin, cefamandole, ceftazidime, ceftriaxone, cefuroxime, and cefotaxime. Positive responses were obtained in 60 of the patients (78.9 %) and the authors concluded that skin testing at a cephalosporin concentration of 

2 mg/ml is a useful tool for evaluating immediate reactions to this p-lactam. 

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. 

---

The diagnostic of immediate-type allergy by skin tests with cephalosporins has been attempted by several groups, but, as already discussed above, does not yield very satisfactory results. Theoretically, it would be much more appropriate to use preformed conjugates of cephalosporins with polylysine. The hemagglutination... 

The true incidence of allergic sensitization due to cephalosporins alone is difficult to assess, since in most patients treated with cephalosporins, the immune status for penicillin sensitivity before treatment is not objectively known and assessed. The general clinical impression is that in patients sensitized to benzyl-penicillin, overt allergic clinical reactions do not occur in more than 10%-20% of those subsequently treated with cephalosporins. The rate of adverse reactions may, however, be higher than suspected. In healthy volunteers given cephalothin and ce-phapirin intravenously, an unexpectedly high rate of reactions was experienced, and five patients developed skin hypersensitivity detected by skin test with PPL. 

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. 

For penicillin-allergic (nonanaphylactoid type) patients cefazolin 6 g/24 hours IV in 3 equally divided doses 6 IB Consider skin testing for oxacillin-susceptible staphylococci and questionable history of immediate-type hypersensitivity to penicillin cephalosporins should be avoided in patients with anaphylactoid-type hypersensitivity to P-lactams vancomycin should be used in these cases ... 

Patients with a history of a reaction to penicillin are advised not to receive cephalosporins if they can be avoided. Patients who have negative penicillin skin tests or experienced only mild cutaneous reactions, such as macu-lopapular rashes, have a low risk of serious reactions to cephalosporins. 

If a patient has a mild, delayed allergy to penicillin, first-generation cephalosporins (such as cefazolin) are effective alternatives, but they should be avoided in patients with a history of immediate-type hypersensitivity reactions to penicillins (see Table 109-6). The potential for a true immediate-type allergy should be assessed carefully, and a penicillin skin test should be conducted before giving antibiotic treatment to any patient claiming an allergy. 

Immunologic Of 85 patients with a history of penicillin allergy and positive penicillin skin tests 5 (6%) had an adverse drug reaction to a cephalosporin compared with 5 (0.7%) of 726 patients with a history of penicillin allergy but negative penidllin skin tests [7. Presumed IgE-mediated adverse reactions to the cephalosporins occurred in 2 (2%) of the former compared with only 1 (0.1%) of the latter. 

Park MA, Koch CA, Klemawesch P, Joshi A, Li JT. Increased adverse drug reactions to cephalosporins in penicillin allergy patients with positive penicillin skin test. Int Arch Allergy Immunol 2010 153 (3) 268-73. 

Fig. 5.17 Cephalosporins with a methoxyimino group in the R1 side chain responsible for skin test reactivity in a patient who experienced anaphylaxis to cefuroxime axetil. Oxacillin, which contains a methyl-substituted isoxazolyl group, a bioisosteie of the methoxyimino group, was also skin test-positive in the patient. Two-dimensional stmc-tures of the four cross-reacting cephalosporins and oxacillin are shown with the methoxyimino groups of the former...

Adverse effects Aztreonam is relatively nontoxic, but it may cause phlebitis, skin rash, and occasionally, abnormal liver function tests. Aztreonam has a low immunogenic potential and shows little cross-reactivity with antibodies induced by other p-lac-tams. Thus aztreonam may offer a safe alternative for treating patients allergic to penicillins and/or cephalosporins. 

Direct skin contact of the veterinarian with animal medications has probably diminished since the 1970s in many countries. Antibiotics (and other medications) used in veterinary medicine and also animal feed are mainly the same as in human medicine, e.g., penicillins, cephalosporins, macrolides, tetracyclines, quinol-ones, sulfas, trimethoprim, antifungals. In addition, other substances have been used in animals only, e.g., penethamate, tylosin, spiramycin, furazolidone. Many antimicrobials are contact sensitizers and may cause contact dermatitis at low concentrations. No routine series for patch testing can be recommended because of the risk of active sensitization. Patch testing should be done with the particular medications with which the veterinarian has been in contact directly or via fodder. Contact urticaria from several antibiotics and disinfectants has also been reported (Hannuksela 1997b Kanerva 1997). 

---