Cross-reactivity and tolerability of imipenem in patients with delayed-type, cell-mediated hypersensitivity to beta-lactams.

BACKGROUND: Administration of imipenem-cilastatin to patients with IgE-mediated hypersensitivity to beta-lactams has always been considered potentially harmful. Recent studies have demonstrated the tolerability of carbapenems (imipenem-cilastatin and meropenem) in patients with IgE-mediated hypersensitivity to beta-lactams; there are no studies on this topic regarding patients with cell-mediated allergy to beta-lactams. The aim of this study is to assess cross-reactivity and tolerability of imipenem in patients with cell-mediated allergy to beta-lactams.

METHODS: From our database we selected 73 patients with cell-mediated allergy to beta-lactams, diagnosed by means of immediate-type skin tests, delayed reading intradermal tests, patch tests and detection of specific IgE. Patients with negative patch tests with imipenem-cilastatin underwent an intramuscular test dosing.

RESULTS: Our patients had a total of 94 nonimmediate reactions to penicillins. All patients had positive patch tests and/or delayed reading intradermal tests for at least one of the penicillin reagent tested and negative immediate-type skin tests and specific IgE. Four patients out of 73 had a positive patch tests to at least one penicillin reagent and imipenem-cilastatin showing cross-reactivity. Sixty-four patients underwent the imipenem-cilastatin intramuscular test dosing and none of them had a clinical reaction.

CONCLUSIONS: Our rate of cross-reactivity between imipenem-cilastatin and other beta-lactams was 5.5%. This result is different from previous findings and this may be explained by the fact that we investigated patients with cell-mediated allergy to beta-lactams. Patients with cell-mediated allergy to beta-lactams should undergo patch tests and a tolerance challenge test before treatment with imipenem-cilastatin.