[In vitro study on the problem of optimal gentamicin therapy in leukopenic patients: short injections or parenteral infusions?].

Killing curves of Pseudomonas aeruginosa were performed in an in vitro system simulating in-vivo gentamicin kinetics, i.e. decay of the antibiotic concentration with a 2.1 h halflife time. Minimal inhibitory concentrations (MIC) of gentamicin killed 99.999% of the initial Pseudomonas inoculum whereas 99.99% were killed at a continuously falling gentamicin concentration (starting from the MIC level) in the same period of time. Regrowth of persistent germs occurred only after 6 hours in cultures exposed to falling gentamicin concentrations, and after 8 hours in cultures kept at the MIC. Thus, a postulated superiority of gentamicin infusions over intermittent gentamicin therapy could not be demonstrated in vitro. Intervals between bolus injections of gentamicin should probably not be longer than 6 hours.