and oral administration. Pharmacokinetics of ofloxacin after parenteral

The concentrations in serum of each volunteer werecorrected according to the actual amount of drug given.Sampling. Samples for assay of serum antibiotic concen-trations were taken from a contralateral vein at 0, 5, 10, 20,30, 45, 60, 90, and120minandat 3, 4, 6, 8, 10, 12, 24, 32, 48,and 72 h after the end ofi.v. and oral administration. Bloodspecimens were centrifuged at 4°C after clotting at roomtemperature. All samples were frozen at -70°C and assayedduringthe following 3 months. Urine sampleswerecollectedbefore the first dose andfrom0to 3, 3 to 6, 6 to 12, 12 to 24,24 to 48, and 48 to 72 h after dosing.Protein binding. Protein binding in serumwas determinedat different concentrations between 0.3 and 2.1 mg/liter bythe micropartition MPS-1 systemfor separation offree fromprotein-bound solutes (Amicon GmbH,Witten, Federal Re-public of Germany). Separation was done at 22°C, andincubations were done at 37°C. Results were not correctedfor nonspecific binding ofthe membrane.High-performance liquid chromatography. Ofloxacin andthe metabolites demethyl-ofloxacin and ofloxacin-N-oxidewere determined by high-performance liquid chromatogra-phy. Basically, the method consists of reverse-phase chro-matography and fluorimetric detection (6). The stationaryphase was Nucleosil 5C18 (Macherey & Nagel, Duren,Federal Republic of Germany) used at room temperature.The detector (Schoeffel FS 970; Kratos, Inc., Karlsruhe,Federal Republic of Germany) was operated under thefollowing conditions: excitation, 295 nm; emission cutoff,418 nm; sensitivity range, 0.05 to 0.20 FA. Fluorescenceyields of the demethyl and N-oxide metabolites were 0.95and0.77relative to ofloxacin. Detection limits ofthe methodwere 0.02 mg/liter in serum and 0.2 mg/liter in urine forofloxacin andits twometabolites. Precision fromday to day