Adverse Effects of the Fluoroquinolones

Data on adverse reactions due to the quinolone antibacterial agents--ciprofloxacin, ofloxacin, pefloxacin, norfloxacin, and enoxacin--observed in a patient sample of approximately 30,000 are reviewed. Overall rates of adverse reactions were 4.0%-8.0%, and adverse reactions necessitated discontinuation of therapy in 1.0%-2.6% of patients. Patterns of organ-system involvement and of signs and symptoms were quite similar, with gastrointestinal effects predominating (nausea, vomiting, diarrhea, or abdominal pain in 1.0%-5.0% of the patients), followed by effects on the central nervous system (dizziness, headache, and/or insomnia in 0.1%-0.3% of the patients) and skin (0.5%-2.2% of the patients). Elevation in levels of hepatic enzymes occurred in 1.8%-2.5% of the patients, azotemia in 0.2%-1.3%, and eosinophilia in 0.2%-2.0%. These adverse effects were reversible after drug withdrawal and were generally not dose-dependent. Within the constraints of the relatively small number of well-documented patients and the unique mechanism of action of these antimicrobial agents, the safety profile of these drugs seems to make them acceptable for use when their administration is well directed and specific. In addition, close surveillance for new phenomena should be maintained.