Specific drug interaction studies have not been conducted with ophthalmic ciprofloxacin. However, the systemic administration of some quinolones has been shown to elevate plasma concentrations of theophylline, to interfere with the metabolism of caffeine, and to enhance the effect of the oral anticoagulant, warfarin, and its derivatives. Transient elevation in serum creatinine has been reported in patients receiving cyclosporin concomitantly with systemic ciprofloxacin.