A COMPARATIVE-STUDY OF OFLOXACIN AND CIPROFLOXACIN ERYTHROCYTE DISTRIBUTION

The present work deals with the in vitro and in vivo distribution of o floxacin and ciprofloxacin in erythrocytes. In vitro studies were carr ied out in standard solutions prepared using fresh blood for a concent ration range between 100 and 0.25 mu g mL(-1). A 5 mg kg(-1) bolus dos e was administered to rabbits and erythrocyte and plasma kinetics were determined over 8 h. A linear model was used to establish the relatio nship between plasma and erythrocyte concentrations of both quinolones in vitro. The mean partition coefficient values obtained were 1.04 +/ - 0.02 and 1.32 +/- 0.03 for ofloxacin and ciprofloxacin, respectively . A decrease in the ciprofloxacin partition coefficient was observed a t higher concentrations. Values ranged between 2.54 +/- 0.40 and 1.38 +/- 0.15 as the concentrations increased. The partition coefficients o btained from the linear relationship between plasma and erythrocyte co ncentrations established from the in vivo data were 0.80 +/- 0.58 for ofloxacin and 0.61 +/- 0.30 for ciprofloxacin. In vivo plasma and eryt hrocyte data analysis was performed by a deconvolution method and the theoretical transfer curves in erythrocytes were estimated. The distri bution of both quinolones to erythrocytes is very rapid, probably due to a high permeability of erythrocyte membranes to these drugs. This w as also confirmed by the parallelism between plasma and erythrocyte ki netics. (C) 1998 John Wiley & Sons, Ltd.