Ofloxacin levels after intravitreal injection - Effects of trauma and inflammation

Purpose: This study was carried out to get an insight into the ofloxacin el imination after intravitreal injection in rabbits. We also studied the effe cts of trauma and inflammation on the vitreous ofloxacin levels after intra vitreal injection of ofloxacin. Methods: A penetrating eye injury in the ri ght eye was inflicted on 24 rabbits and another 12 animals were used as con trol. A standardized intraocular inflammation was induced by intravit-real injection of a suspension of Staphylococcus aureus in half of the traumatiz ed eyes. Ofloxacin (200 mu g/0.1 ml) was injected into the midvitreous cavi ty of both traumatized and control right eyes, and samples were obtained at 2, 8, 24 and 48 h after injection. Drug concentrations were measured using high-pressure liquid chromatography analysis. Results: Vitreous levels of ofloxacin were above the MIC90 at 2 and 8 h in all groups for most of the c ommon microorganisms causing endophthalmitis and also at 24 h in traumatize d-infected eyes. At the second hour, the mean vitreous concentrations of of loxacin both in traumatized and traumatized infected eyes were lower than t hat in the control eyes (p < 0.05). At 8 h, the mean vitreous concentration s of ofloxacin in the traumatized and in the traumatized-infected eyes were higher than that in the control eyes (p < 0.05). At 24 h, the mean ofloxac in concentration was higher in the traumatized-infected eyes than that in c ontrol (p < 0.01) and traumatized eyes (p < 0.05), and also higher in the t raumatized eyes than that in the control eyes (p < 0.05). The mean ofloxaci n concentrations in the traumatized and traumatized-infected eyes were sign ificantly higher (p < 0.01) than those in the controls at 48 h. The elimina tion half-life of ofloxacin in the control eyes was 5.65 h and trauma and i nflammation prolonged the half-life to 9.47 and 9.72 h, respectively. Concl usion: Clearance of ofloxacin is fast and appears to be reduced by trauma a nd inflammation. Therapeutic drug levels in traumatized-infected eyes were maintained up to 24 h. This may be an important pharmacokinetic advantage i n treating endophthalmitis unless the dose used has local toxicity and allo ws a longer dose interval when the dose is repeated.