Effect of pazufloxacin mesilate on the serum concentration of theophylline.

We studied the effect of pazufloxacin mesilate (T-3762), a new fluoroquinolone for intravenous administration, on the serum concentration of theophylline. Evaluation consisted of comparisons of serum levels of theophylline (when it was given alone, as a control), with serum levels of theophylline when T-3762 was given concomitantly. We measured the serum concentrations and the urinary excretion rates of theophylline in healthy adult male volunteers who were given theophylline for 5 days, followed by an i.v. infusion of T-3762. Blood and urine samples were investigated on the third and fifth days after the concomitant dosing with T-3762, to compare the serum levels and urinary concentrations of theophylline with the control values. We found that the serum concentration and the urinary excretion rates of theophylline on the fifth day after concomitant dosing with T-3762 were significantly increased compared with the levels when the volunteers had been given theophylline alone.