Vitreous and Aqueous Penetration of Orally Administered Trimethoprim-Sulfamethoxazole Combination in Humans

To determine the penetration of orally administered trimethoprim (TMP)-sulfamethoxazole (SMX) into the aqueous and vitreous cavity of noninflamed human eyes. Nine adult patients undergoing cataract surgery and 10 adult patients undergoing pars plana vitrectomy were given 3 doses of oral TMP-SMX every 12 hours before the surgery. Aqueous and blood samples were collected from patients undergoing cataract surgery; vitreous and blood samples were collected from patients undergoing vitrectomy. The levels of TMP and SMX were analyzed using high-performance liquid chromatography and were compared with the mean minimum inhibitory concentrations (MIC) of potential ocular pathogens. TMP-SMX was present in all samples. Among eyes undergoing cataract surgery, the mean concentrations of TMP in aqueous and blood were 0.341 ± 0.141 μg/mL (mean ± SD) and 1.501 ± 0.433 μg/mL and of SMX were 5.259 ± 0.929 μg/mL and 11.835 ± 2.100 μg/mL, respectively. Among eyes undergoing vitrectomy, the mean concentrations of TMP in vitreous and blood were 1.864 ± 0.807 μg/mL and 4.591 ± 2.979 μg/mL and of SMX were 5.910 ± 2.705 μg/mL and 39.289 ± 15.469 μg/mL, respectively. MIC levels were achieved against many bacterial pathogens, including methicillin-resistant Staphylococcus aureus. TMP-SMX penetrates both the aqueous and vitreous cavities when given orally. The components reach therapeutic inhibitory concentrations in the ocular cavity against many potential pathogens.