Treating acute sinusitis
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Editor, – In the article 'Treating acute sinusitis' (Aust Prescr 2000;23:39-41), the author stated that 'patients allergic to penicillin should be treated with either trimethoprim-sulfamethoxazoleor cefaclor'. Because cefaclor is a cephalosporin, the statement raises questions about cross-sensitivity with penicillins.
In my experience, substantial numbers of clinicians are still confused about the possibility of cross-sensitivity between various beta-lactam antibiotics. I think this topic deserves clarification.
It is well known that cephalosporins might show cross-sensitivity with penicillins. The frequency of cross-reactions is uncertain, but is probably relatively low, around 5-10% (in immunological studies up to 20%). It seems that the patients with a history of mild reactions to penicillins are at low risk of developing an allergic reaction following administration of a cephalosporin. On the other hand, many authorities recommend that if a patient has ever experienced a severe allergic reaction (anaphylaxis) to penicillin, it is strongly advisable not to give a cephalosporin.
Pharmacologist and Clinical Pharmacologist in Training
Department of Phamacology, Medical Faculty
Center for Clinical and Experimental Pharmacology
Clinical Hospital Centre