Ciprofloxacin Prolonged‐Release Tablets Do Not Affect Warfarin Pharmacokinetics and Pharmacodynamics

The purpose of this study was to determine whether the pharmacokinetics of warfarin and ciprofloxacin PR (a prolonged-release formulation of ciprofloxacin) were altered after coadministration. Eighteen healthy male volunteers were given a single oral 7.5-mg dose of warfarin, a single oral 500-mg dose of ciprofloxacin PR, or both drugs administered together in a randomized, open-label, 3-way crossover study. Ciprofloxacin concentrations, warfarin (R)- and (S)-enantiomer concentrations, prothrombin time, and activated partial thromboplastin time were measured over 120 hours following study drug administration. There were no significant differences in pharmacokinetic or pharmacodynamic parameters among treatments. A slightly greater value of half-life for (R)-warfarin was observed when coadministered with ciprofloxacin PR compared with warfarin administered alone (52.6 vs 50.1 hours, P = .029). This difference is not considered clinically relevant, because the values remain similar. These results show that warfarin pharmacokinetics and pharmacodynamics are not altered with concomitant administration of ciprofloxacin PR.