Comparison of the in vitro effects of amoxicillin and ampicillin on the polymorphonuclear neutrophil respiratory burst.

OBJECTIVES: The aim was to compare the in vitro effects of amoxicillin and ampicillin on the oxidative metabolism of polymorphonuclear neutrophils (PMNs). METHODS: Superoxide radical anion production by PMNs, stimulated or not by various exogenous stimulants and in contact with increasing antibiotic concentrations, was measured using spectrophotometric methods. RESULTS: Whereas a pro-oxidative action of amoxicillin on PMNs was obtained without exogenous stimulation or with opsonized zymosan (OZ), the O(2)(-) production by PMNs incubated with ampicillin did not increase significantly. CONCLUSIONS: This amoxicillin pro-oxidative effect could be due to the activation of the PMN NADPH oxidase, to its induction by a membrane effect or via the OZ pathway. It probably reinforces amoxicillin intrinsic bactericidal action and might partly explain the severe rashes sometimes occurring with amoxicillin treatment.