Penetration of gentamicin and ofloxacin in human vitreous after systemic administration.

BACKGROUND: Data on the penetration of antibiotics into the aqueous humor in man and animals, as well as on the intravitreal penetration in animals, are numerous. Data on their intravitreal penetration in humans, however, are sparce. The intravitreal penetration of gentamicin was studied in different ocular pathologies to see whether these alter the vitreal pharmacodynamics. The intravitreal penetration of ofloxacin, a fluoroquinolone, was determined to see whether levels sufficient to treat infectious endophthalmitis could be reached.
METHODS: The intravitreal penetration of gentamicin and ofloxacin was studied in patients undergoing pars plana vitrectomy for various ocular pathologies. Those with recent hemorrhages and those already receiving general antibiotic treatment were excluded.
RESULTS: Gentamicin was found to penetrate the vitreous very poorly. No difference could be found between the various pathologies: trauma, diabetes, proliferative vitreoretinopathy, longstanding vitreous hemorrhage and macular pucker gave the same poor penetration. The ofloxacin levels were higher but did not reach the MIC90 levels of most organisms involved in bacterial endophthalmitis.
CONCLUSION: The hemato-ocular barrier is more difficult to cross than originally thought. Different ocular pathologies do not alter the ocular barrier substantially. Ofloxacin alone does not seem to be sufficient for the treatment of established bacterial endophthalmitis.