Estimation of Tear Film Concentration of Oral Ciprofloxacin in Patients With Bacterial Keratitis

Aims: To estimate the tear film concentration of oral ciprofloxacin in patients with bacterial keratitis and evaluate its correlation with various clinical factors. Method: This prospective intraindividual study enrolled 52 patients (104 eyes), each with unilateral, microbiologically confirmed bacterial keratitis (n=52 eyes); the fellow eye (n=52 eyes) served as the healthy control. The etiology of keratitis was confirmed by corneal scraping followed by detection of bacteria on Gram stain and bacterial culture. In addition to empirical therapy with topical fortified cefazolin 5% and tobramycin 1.3%, changing drugs if necessary, according to the antibiotic sensitivity report, these patients received oral ciprofloxacin 500 mg BD for 5 days. Tear samples were collected from infected and noninfected eyes, respectively, 3 hr after the morning dose of day 5. These samples underwent liquid chromatography and mass spectrometry to estimate concentration of ciprofloxacin in tear film. Result: Staphylococcus epidermidis was the most prevalent organism in our study (28.85%). The median ulcer area was 24 (4, 72) mm 2 . The median concentration of ciprofloxacin in tear samples from infected eyes was 547 (10.9, 3,490) ng/mL. In the noninfected eyes, the median concentration was 461 (3.86, 1730) ng/mL. The median concentration of ciprofloxacin in infected eyes was comparable with the minimum inhibitory concentration (MIC) for Staphylococcus species. Drug concentration in tear film had a strong positive correlation with ulcer area (Spearman rho=0.957; P =0.02) but weak positive correlation with the presence of infection (Spearman rho=0.245; P =0.08). Conclusion: Oral ciprofloxacin reaches tear concentration similar to the reported MIC of staphylococcus species, therefore is a promising adjuvant to topical therapy in staphylococcal keratitis. Further larger scale, comparative studies are warranted to ascertain the same.