Cefotetan‐induced immunologic thrombocytopenia

Profound thrombocytopenia accompanied by a severe coagulopathy developed in an elderly female patient being treated with cefotetan while undergoing surgery for closure of a perforated gastric ulcer. During the acute phase of the bleeding diathesis, the patient had a platelet count of 12 × 109/1, a prothrombin time of 88 s (normal 10.0–11.8 s) and a PTT of 105 s (normal 23.0–37.0 s). Potent IgG cefotetan‐dependent anti‐platelet antibodies, which also were weakly reactive with ampicillin, were detected in the patient's serum using immunofluorescence and a recently developed protein A–agarose rosette forming assay. Unlike typical cephalosporin‐ and penicillin‐induced antibodies that react with cells pretreated with drug, this antibody only reacted with platelets in the presence of exogenous drug. Failure of the antibody to react with drug‐coated platelets suggests the possibility that, in this patient, sensitization to cefotetan involved mechanisms other than formation of typical hapten–carrier complexes normally described for members of the cephalosporin family of antibiotics. This appears to be the first definitive report that cefotetan, or any other cephalosporin derivative, can induce immunologic thrombocytopenia.