Allergy to cloxacillin with normal tolerance to amoxicillin and cefuroxime.
BACKGROUND
Cloxacillin is a semisynthetic penicillin widely used in nonmethicillin resistant Staphylococcus aureus infections. Several hypersensitivity reactions to cloxacillin have been reported, although IgE-mediated allergic reactions to the drug are rare and there is little information about possible tolerance to other semisynthetic penicillins or cephalosporins in patients with cloxacillin allergy. We present 2 patients with demonstrated IgE-mediated allergy to cloxacillin and tolerance to amoxicillin and cefuroxime.


METHODS
Case 1. A 47-year-old woman began treatment with cloxacillin due to acute cellulitis. After ingesting 500 mg of the drug, she experience generalized maculopapular eruption and facial angioedema. Case 2. A 55-year-old woman presented an episode of acute urticaria and labial angioedema 60 minutes after ingesting 500 mg of cloxacillin for a skin abscess.


RESULTS
Skin prick tests were positive to cloxacillin in case 1 and negative in case 2. However, an intradermal test was positive to cloxacillin (2 mg/ml) in case 2. Simple-blind oral challenge tests with amoxicillin (1 g) and cefuroxime (500 mg) were well-tolerated by both patients.


CONCLUSIONS
We present 2 patients allergic to cloxacillin with normal tolerance to other betalactam antibiotics, confirming that cross-reactivity among these antibiotics seems to be uncommon. Complete allergy study, including an oral challenge test, should be considered in these patients.
Unit of Allergy, Hospital Universitario de Getafe, Madrid, Spain. jdort@mixmail.com
J
J
Domínguez-Ortega
J C
JC
Martínez-Alonso
M C
MC
Marcos-Pérez
C
C
Kindelan
A
A
Frades
D000038:Abscess / Q000188:drug therapy; D000658:Amoxicillin; D000799:Angioedema / Q000139:chemically induced*; D002444:Cefuroxime; D002481:Cellulitis / Q000188:drug therapy; D003023:Cloxacillin / Q000009:adverse effects* / Q000627:therapeutic use; D003875:Drug Eruptions / Q000209:etiology*; D005260:Female; D006801:Humans; D007428:Intradermal Tests; D008875:Middle Aged; D016037:Single-Blind Method; D012882:Skin Tests
D000658:Amoxicillin; D002444:Cefuroxime; D003023:Cloxacillin