Cephalosporins Allergy

CEPHALOSPORINS ALLERGY

Cephalosporins are -lactam antibiotics that differ from the penicillins in that the B ring is a 6-membered dihydrothiazine ring.

Cephalosporin antibiotics are widely prescribed for common infections such as bronchitis, otitis media, pneumonia, and cellulitis. They are also administered as first-line prophylaxis for many types of surgical procedures. A relative contraindication to these agents is a history of allergy to penicillin.

Cross-Reactivity with Penicillin

Because penicillin-related compounds are produced by the cephalosporium mold, early cephalosporin antibiotics contained trace amounts of penicillin. Thus, penicillin contamination may have led early studies to cephalosporins allergy and penicillin allergy to overestimate the degree of cross-reactivity.

Studies suggest that the risk of cephalosporins allergy in patients with a history of allergy to penicillin may be up to eight times as high as the risk in those with no history of allergy to penicillin. The studies also suggest that patients with a history of penicillins allergy but negative skin tests are not at increased risk for cephalosporins allergy. Thus, testing for a penicillin allergy may be useful in patients with a history of allergy to penicillin who require cephalosporin therapy.

The product label for all cephalosporin antibiotics states,

Before therapy with [the cephalosporin] is instituted, careful inquiry should be made to determine whether the patient has had previous hypersensitivity reactions to [the cephalosporin], other cephalosporins, penicillins, or other drugs. If [this product] is to be administered to penicillin-sensitive patients, caution should be exercised because cross-hypersensitivity among beta-lactam antibiotics has been clearly documented and may occur in up to 10% of patients with a history of penicillin allergy.

Tests for Cephalosporins Allergy

Attempts to develop a skin test for cephalosporins allergy have been unsuccessful, and skin testing with the native drug alone has little predictive value. No anti-cephalosporin IgE antibody assays are available clinically. Skin tests for allergy to penicillin can be useful in evaluating patients with a history of cephalosporins allergy.

Recommendations for Patients with Cephalosporins Allergy

If the skin test is negative, they can receive penicillin or cephallosporin; if it is positive, they should either receive an alternative medication or undergo desensitization to penicillin.

A patient who has had cephalosporins allergy should not receive that cephalosporin again. Cross-reactivity (or the absence of it) between a cephalosporin and other beta-lactam antibiotics can be explained in part by the structure of the side chains.

Test dosing consists of the administration of a small dose of the drug, less than the dose that potentially would cause a serious reaction, followed by relatively large incremental increases in the dose until the full therapeutic dose is given. The administration of a cephalosporin to a patient who is potentially allergic to that drug is hazardous and is not recommended.

Conclusions

Patients with a history of cephalosporins allergy 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 such cephalosporins allergy. The majority of these patients have negative tests and should not be at increased risk for a reaction to cephalosporins.