Lachrymal Concentration of Norfloxacin after a Single Ocular Instillation in Humans

Lachrymal concentrations of the fluoroquinolone norfloxacin were studied in 30 subjects (aged 24-35 years) after a single ocular instillation (0.3% solution, 50 ul) in comparison with ofloxacin instilled at the same dose. Lachrymal levels were measured by high performance liquid chromatography (HPLC). Lachrymal peak levels were comparable 5 min after instillation but norfloxacin appeared to have a longer elimination half-life than ofloxacin. The AUC (area under the curve) for norfloxacin was therefore higher than for ofloxacin (35.9 and 10.7 mg* min/ml, respectively). These data suggest that norfloxacin may have higher corneal retention than ofloxacin, so this antibiotic may be indicated in superficial infections dependent on fluoroquinolone-sensitive bacteria.