Prophylactic Antibiotic Management of Surgical Patients Noted as "Allergic" to Penicillin at Two Academic Hospitals.

We studied prophylactic antibiotics administered at 2 academic medical centers during a 6-year period where a cephalosporin was indicated but an "allergy" to penicillin was noted. Another drug (typically vancomycin or clindamycin) was substituted approximately 80% of the time; this occurred frequently even when symptoms unrelated to acute hypersensitivity were listed. In >50% of cases, the reaction was either omitted or vague (e.g., simply "rash"). Given the estimated 1% cross-reactivity between penicillins and cephalosporins with similar R1 side chains, many of these patients could have received either the prescribed cephalosporin or another cephalosporin with a different R1 side chain.