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.
Domínguez-Ortega
J
J
Unit of Allergy, Hospital Universitario de Getafe, Madrid, Spain. jdort@mixmail.com
Martínez-Alonso
J C
JC
Marcos-Pérez
M C
MC
Kindelan
C
C
Frades
A
A
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