Cetuximab use without chronic antihistamine premedication
13521 Background: Cetuximab is a human-murine chimeric monoclonal antibody against EGFR with approximately a 3% reported incidence of severe (≥ grade 3) anaphylactoid reactions. The overwhelming majority of such reactions have been reported with the initial dose of cetuximab. Diphenhydramine (Benedryl)or a related antihistamine is often given as a premedication for cetuximab, however this may cause fatigue or other side effects. Most early clinical trials of cetuximab permitted investigator discretion in use of premedication beyond the initial cetuximab dose. Methods: We obtained an IRB waiver of authorization to review the records of patients treated with cetuximab at Memorial Sloan Kettering Cancer Center for the first year of commercial availability of cetuximb (Feb, 2004 through Feb, 2005). Computerized pharmacy records were reviewed to identify all patients who were treated with cetuximab (outside of a clinical trial) and use of premedication was then evaluated. Records of institutional adverse event reports regarding chemotherapy administration were reviewed, and, any moderate or severe/life-threatening reactions were evaluated for presence or absence of concurrent premedication. Results: As per our institutional guidelines, all patients received 50 mg of diphenhydramine prior to the initial loading dose of cetuximab, and 25 mg of diphenhydramine prior to the second dose. While there was inconsistency in terms of cessation of diphenhydramine, overall a total of 115 patients received one or more doses of cetuximab without premedication. A total of 746 doses of cetuxmab without diphenhydramine premedication were given over this time period. No severe/life-threatening reactions to cetuximab occurred during these doses given without premedication. Conclusions: Omission of diphenhydramine premedication after the initial two doses of cetuximab is our current institutional practice, and appears not to alter the safety profile of cetuximab. Considering the side effects of diphenhydramine, routine long tern use of antihistamine premedication with cetuximab administration does not appear to be warranted. [Table: see text]