Cross-reactivity between penicillins and cephalosporins: clinical and immunologic studies

Nineteen well-characterized penicillin-allergic patients were investigated for their sensitivity to cephalosporins containing potentially cross-reactive side chains. All patients were administered cephamandole parenterally and, if this was tolerated, a course of oral cephaloridine was administered. Only two patients responded to the cephamandole; none of the remaining patients reacted to cephaloridine. Benzylpenicilloyl RAST-inhibition studies with sera from three subjects who had not reacted to the cephalosporins demonstrated that cephamandole linked to proteins was capable of recognizing benzylpenicilloyl-specific IgE antibody. It is concluded that consideration of side chain structures can help to predict possible cross-reactions between penicillins and cephalosporins, but carefully controlled challenge tests are advisable before penicillin-allergic patients are treated with cephalosporins. In relation to cross-reacting potential, in vitro experimental studies are difficult to interpret and may in some circumstances overestimate the risk.