Drug interactions with fluoroquinolones.

The fluoroquinolones are a new class of antimicrobial agents that are now widely prescribed for a number of bacterial infections. Because of their complex pharmacokinetics, there is a potential for several types of drug interactions. Currently, only two drug interactions have been well studied. These involve a decrease in absorption when fluoroquinolones are given in combination with multivalent metal cations and an inhibition in the metabolism of methylxanthines by fluoroquinolones such as ciprofloxacin, enoxacin, and norfloxacin. These drug interactions can be easily avoided. Significant decreases in the absorption of fluoroquinolones by metal cations can be prevented by staggering the doses of these drugs. To avoid alterations in methylxanthine metabolism, newer fluoroquinolones, such as lomefloxacin, ofloxacin, and temafloxacin, should be utilized; alternatively, theophylline serum levels can be carefully monitored. Several other potentially serious drug interactions involving cyclosporine, warfarin, and nonsteroidal anti-inflammatory drugs have been reported, but additional investigations are required before their overall clinical significance can be fully determined. Since the use of fluoroquinolones will continue to escalate over the next decade, continued patient surveillance is necessary so that potential drug interactions can be recognized, described, and prevented.