Intraocular penetration of rifampin after oral administration.

Rifampin, the most potent anti-staphylococcal drug known, was examined for its penetration into the aqueous and vitreous of rabbits after a single oral dose of 150 mg, 300 mg, or 600 mg. Maximum levels after the 150 mg dose were achieved at 4 h and were 4.2 micrograms/ml in the aqueous and 2.2 micrograms/ml in the vitreous. After the 300 mg dose, maximum levels were also achieved at 4 h, and were 5.0 micrograms/ml in the aqueous and 2.6 micrograms/ml in the vitreous. The 600 mg dose produced maximum levels at 6 h after administration, with 20.0 micrograms/ml in the aqueous and 15.2 micrograms/ml in the vitreous. These levels exceed the minimum inhibitory concentration for many microorganisms and suggest additional investigation into possible applications of systemic rifampin in the prophylaxis and treatment of bacterial endophthalmitis.