Safety Overview

This chapter reviews the toxicity, adverse effects, and drug interactions of the quinolones. The fluoroquinolones are usually considered as relatively safe and well tolerated drugs. Under therapeutic conditions, no uniform life-threatening organ toxicity is known that would restrict their clinical use. However, in certain cases, unexpected adverse effects occurred after treatment with the fluoroquinolones as observed before with antimicrobials from other classes. Stained teeth in children due to tetracyclines, effects of certain cephalosporins on blood clotting, and severe reactions seen with the fluoroquinolone temafloxacin were noticed only several months or even years after launch of the drug. The fluoroquinolones temafloxacin, trovafloxacin, and grepafloxacin were taken off from the market due to rarely occurring severe adverse reactions. The use of temafloxacin was associated with a syndrome of hemolysis, renal failure, and thrombocytopenia. Due to this toxicity, the drug was withdrawn from the market shortly after approval for its clinical use in 1992. The use of trovafloxacin was associated with severe hepatic reactions in some rare cases. A total of 140 patients with severe hepatic reactions came into surface after the drug was prescribed worldwide to approximately 2.5 million patients. Another quinolone that was taken off the market in 1999 was grepafloxacin. Due to its effect on cardiac repolarization, manifested as QT interval prolongation on the electrocardiogram, some patients were considered at risk of torsade de pointes when treated with grepafloxacin.