Intraocular penetration of dicloxacillin in experimental animals.

Adult rabbits were given single intravenous injections of 25 mg. per kilogram of sodium dicloxacillin. At intervals of time ranging from 15 minutes to 8 hours after injection, primary or secondary aqueous humor was aspirated from each eye. At the same time, a specimen of cardiac blood was withdraion. Other animals were given subconfunctival injections of 50 mg. of dicloxacillin. Aqueous humor was aspirated one and 4 hours after injection. Assay of intraocular fluids and serum for antibiotic activity was by the disc-plate inhibition method with Sarcina lutea FDA 1001 as test organism. Following intravenous injection, dicloxacillin failed to penetrate the intact blood-aqueous humor barrier. However, excellent penetration was obtained into secondary aqueous humor, the resulting high dicloxacillin concentrations remaining in the intraocular fluids for some 4 to 8 hours. High antibiotic concentrations were present in primary aqueous humor one and 4 hours after subconjunctival injection of dicloxacillin. Although dicloxacillin is highly bound to plasma protein, high titers are attainable in secondary aqueous humor. The presence of two chlorines on the isoxazolyl group which enhances movement of this compound across membranes in other areas (gut) also facilitates movement across the disturbed blood-aqueous humor barrier into the intraocular fluids.