Abstract
We evaluated the systemic absorption of ofloxacin eyedrops in humans and their availability in the tear film. Serum, urine, and tear film concentrations of ofloxacin were measured in 30 healthy women topically treated with 0.3% ofloxacin, in both eyes, four times daily for 10½ days. Serum was collected before the first daily dose on days 1 and 11 and at 18 time points before the second dose. Maximum serum ofloxacin concentrations (1.89 ± 1.13 ng/ml) after 10½ days of topical dosing were more than 1,000 times lower than those reported after standard oral doses of 300 mg ofloxacin. Urine was collected for the 24-h period after the first daily dose on days 1 and 10. Topical ofloxacin was excreted in the urine primarily in unmodified form and recovery rates were significantly higher on day 10 (76.1 ± 41.5%) than on day 1 (56.6 ± 31.6%) (p < 0.05). Both serum and urine data give evidence to accumulations of ofloxacin over a 10½-day period. The low serum concentration at steady state suggests an extremely low potential for producing systemic effects. No systemic side effects attributable to topical ofloxacin were observed. Mild ocular irritation was reported by two patients while under treatment. Tears were collected 4 h after the first treatment on day 11 and at 5, 10, 20, 30, and 40 min after the second treatment. Tear film levels 4 h after dosing (9.16 ± 8.24 μg/g) were higher than the 2 μg/ml MIC90 value (minimum inhibitory concentration against 90% of bacterial strains) reported for ofloxacin against 190 gram-negative and 229 grampositive organisms. Over the 40-min measurement period, concentrations of ofloxacin in the tear film ranged from 5.7 ± 2.4 to 31.0 ± 23.5 μg/g. The ability to maintain tear ofloxacin levels higher than the MIC90 may help account for the excellent clinical effectiveness of ofloxacin.
Published Version
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