Antibiotics and human monocyte function. II. Phagocytosis and oxidative metabolism.

The influence of thirteen commonly used antibacterial drugs on the phagocytic and oxidative burst responsiveness of human blood monocytes in vitro was investigated. Cefotaxime and rifampicin produced a significant inhibition of monocyte oxidative metabolism at therapeutic concentrations with increasing inhibition at higher concentrations. The effect of rifampicin was irreversible, which may reflect intracellular accumulation of the drug. Tetracycline, clindamycin, chloramphenicol and tobramycin at high concentrations produced a significant inhibition of monocyte superoxide anion release after stimulation, whereas normal therapeutic concentrations produced insignificant inhibition. Benzylpenicillin, ampicillin, fusidic acid, metronidazole, ofloxacin, sulfamethoxazole and trimethoprim did not alter monocyte oxidative metabolism in vitro. Phagocytosis of yeast cells was significantly suppressed by high concentrations of tobramycin, but otherwise unaffected by the drugs mentioned. These observations suggest that cefotaxime and rifampicin may interfere with blood monocyte oxidative metabolism in vivo, whereas it can be expected that at normal dosage it is unlikely that the other drugs will affect monocyte phagocytosis and oxidative burst activity.