Penetration of ocular compartments by tetracyclines. II. An experimental study with doxycycline

Using radioactive tracer method the distribution of intravenously injected doxycycline of 7 mg/kg was studied in the rabbit eye. Long-lasting antibiotic concentration of 1 microgram/g or more was measured from all vascularized ocular structures. Vitreous body doxycycline concentration, almost equal to that of aqueous humor, was 0.3 microgram/g. Doxycycline concentration in the cornea exceeded that in the aqueous humor. In all vascularized ocular structures plasma antibiotic concentration was at least once achieved, indicating good penetrability of doxycycline into the tissues. This good penetrability is obviously related to the high lipoidsolubility of doxycycline, whereas its high protein binding is reflected in low concentrations in the aqueous humor.