The Pharmaceutical Journal
Vol 276 No 7400 p560
13 May 2006

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Cephalosporins often safe in patients allergic to penicillin

POEM series

Clinical question What is the evidence regarding the use of cephalosporins in patients with penicillin allergy?

Bottom line The risk of cross-reactivity between penicillin and cephalosporins has been overestimated for second- and third-generation drugs. It is only a significant risk in first-generation cephalosporins that have a similar side chain to penicillin (cefalotin, cefalexin, cefadroxil and cefazolin). With appropriate monitoring clinicians could consider using second- and third-generation cephalosporins in these patients.

Synopsis The author did a comprehensive search of MEDLINE and EMBASE to identify the 101 articles that were used as the basis for this systematic review. The overall rate of rash is approximately 2 per cent. Anaphylaxis is very rare, with a risk between 0.1 per cent and 0.0001 per cent. Clinicians often worry about cross-reactivity between penicillins and cephalosporins, but this only seems to apply to first-generation cephalosporins such as cefalotin, cefaloridine, cefalexin, cefadroxil and cefazolin. No increase in the risk of an allergic reaction is seen in second- and third-generation cephalosporins, including cefprozil, cefuroxime, ceftazidime, cefpodoxime and ceftriaxone. The author speculates that this is because of similar side chains in the chemical structure between penicillins and first-generation (but not second- or third-generation) cephalosporins. Patients with a previous IgE-mediated reaction to penicillin (eg, wheezing, angio-oedema, urticaria, laryngeal oedema or anaphylaxis) should not use first-generation cephalosporins but may be able to safely take second- and third-generation cephalosporins.

Level of evidence 2a (systematic review of cohort studies, with homogeneity)

Reference Pichichero ME. Cephalosporins can be prescribed safely for penicillin-allergic patients. Journal of Family Practice 2006;55:106–12

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