Effect of a new quinolone, sparfloxacin, on the pharmacokinetics of theophylline in asthmatic patients.

Recently, it has become evident that some quinolones affect the processing of theophylline in the human system. The effect of a new quinolone, sparfloxacin, on the pharmacokinetics and metabolism of theophylline was investigated in six asthmatic patients receiving chronic theophylline therapy (a sustained-release theophylline tablet formulation of 200 to 300 mg twice daily at 12-h intervals). To these patients, sparfloxacin (200 mg once daily) was coadministered for 1 week. Plasma and urine samples were analyzed by high-performance liquid chromatography for theophylline and its metabolites. Plasma theophylline concentration-time curves and the urinary excretion of theophylline and its major metabolites before and after coadministration of sparfloxacin were compared. The total body clearance of theophylline after coadministration of sparfloxacin, 42.81 +/- 6.64 ml/h/kg (mean +/- standard error of the mean), was not significantly different from that after the administration of theophylline alone, 47.11 +/- 7.61 ml/h/kg. Also, no significant change in the urinary excretion of theophylline and its metabolites was observed for subjects receiving or not receiving sparfloxacin. These findings indicate that a once-daily dose of 200 mg of sparfloxacin has no significant effect on the pharmacokinetics and metabolism of theophylline and that it would be safe to coadminister this quinolone to asthmatic patients receiving chronic theophylline therapy.