Uptake of ciprofloxacin by human neutrophils.

Ciprofloxacin was concentrated within human neutrophils to between four and seven times the extracellular concentration. Uptake was rapid and dependent on temperature, but not pH. The elution of ciprofloxacin from cells was equally rapid when the extracellular concentration was reduced. Intracellular ciprofloxacin was biologically active. It produced a significant reduction in viable counts of intracellular Staphylococcus, aureus in the presence of extracellular concentrations as low as 0.5 mg/l. The prior ingestion of Staph. aureus by neutrophils appeared to have no effect on ciprofloxacin uptake.