Systemic antibiotic prophylaxis in penetrating ocular injuries. An experimental study.

Intraocular concentrations of systemically administered gentamicin and cefazolin in eyes after a standard penetrating ocular injury were measured to determine the effect of eye injury on ocular pharmacokinetics. Twenty pigmented rabbits were divided into two groups. A standard, 8-mm wound was made at the pars plana of one eye in each animal. Group 1 consisted of 10 rabbits that were treated with cefazolin (75 mg/kg), and Group 2 consisted of 10 rabbits that were given gentamicin (2 mg/kg). Fellow eyes, which sustained no trauma, served as control eyes. All groups received intravenous injections every 8 hours for 72 hours, beginning immediately after repair of the wound. After 72 hours, samples were obtained from the anterior chamber, vitreous cavity, and serum. Standardized bioassays for detection of gentamicin or cefazolin were performed. Significant concentrations of intravitreal cefazolin (9.6 micrograms/ml) and gentamicin (0.60 micrograms/ml) were found in the traumatized eyes in comparison to control eyes (P = 0.0001; P = 0.006). Cefazolin exhibited excellent penetration, achieving concentrations well above minimum inhibitory concentration values for most organisms. Gentamicin levels, however, were well below acceptable therapeutic levels. This study suggests that systemically administered cefazolin can achieve significant intravitreal penetration at minimum inhibitory concentrations after penetrating injury.