Vitreous pharmacokinetics and retinal safety of intravitreal preserved versus non-preserved triamcinolone acetonide in rabbit eyes

Purpose: To compare the intravitreal pharmacokinetic profile of a triamcinolone acetonide formulation containing the preservative benzyl alcohol (TA-BA) versus a preservative-free triamcinolone acetonide formulation (TA-PF), and evaluate potential signs of toxicity to the retina. Methods: A total of 60 New Zealand male white rabbits, divided into two groups, were studied. In the TA-BA group, 30 rabbits received an intravitreal injection of TA-BA (4mg/0.1ml) into the right eye. In the TA-PF group, 30 rabbits received an intravitreal injection of TA-PF (4mg/0.1ml) into the right eye. The intravitreal drug levels were determined in 25 animals from each group by high-performance liquid chromatography (HPLC). The potential for toxicity associated with the intravitreal triamcinolone injections was evaluated in five randomly selected animals from each group by electroretinography (ERG) and by light microscopy. Results: Median intravitreal concentrations of TA-BA (g/ml) were 1903.1, 1213.0, 857.8, 442.0, 248.6 at 3, 7, 14, 21 and 28 days after injection. Intravitreal concentrations of TA-PF (g/ml) were 1032.9, 570.1, 516.6, 347.9, 102.8 at 3, 7, 14, 21 and 28 days after injection. The median intravitreal triamcinolone concentration was significantly higher in the TA-BA compared to the TA-PF group at 7 days post-injection (p<0.05). There was no significant difference between the two groups in median triamcinolone concentration at the other time points evaluated. There was no evidence of toxic effects on the retina in either group based on ERG or histological analyses. Conclusions: Following a single intravitreal injection, the median concentration of triamcinolone acetonide is significantly higher in the TA-BA compared to the TA-PF group at 7 days post-injection. No toxic reactions in the retina were observed in either group.