Aim To characterise the pharmacokinetics of triamcinolone acetonide (TA) in various ocular tissues following a single sub-Tenon injection.
Methods Twenty-one Chinchilla adult pigmented rabbits received sub-Tenon injection of TA (40 mg in 0.4 ml) in their right eyes. Three animals were killed at each designated time points (3 h, 1 day, 3 days, 7 days, 14 days, 21 days and 30 days) and the globes were snap frozen and dissected into aqueous, iris-ciliary body, vitreous, neuroretina and retinal pigment epithelium (RPE)/choroid. The concentrations of TA in the various ocular tissues were analysed using ultra-performance liquid chromatography, coupled with tandem mass spectrometric detection.
Results TA concentration followed a mono-exponential decrease over the study period in all ocular tissues of the injected eyes. The concentration was much higher in the RPE/choroid (892.14±558.11 ng/g at post-injection day 30) than in the other tissues (171.65±136.40 ng/g in neuroretina, 15.65±23.06 ng/ml in vitreous, 3.76±1.79 ng/g in iris-ciliary body, 2.64±0.96 ng/ml in aqueous at post-injection day 30). The TA level in the RPE/choroid had the lowest coefficient of logarithmic regression (0.07 in RPE/choroid, 0.10 in neuroretina, 0.11 in vitreous, 0.17 in iris-ciliary body, 0.18 in aqueous), indicating a 2.6 times slower clearance than in aqueous. The half-life of TA was 10.4 days in RPE/choroid. TA was detectable in the fellow eyes and was also detectable at very low levels in all blood samples during the entire study period.
Conclusion TA was mostly cleared from RPE/choroid and retina in a mono-exponential mode. TA was above the therapeutic level for at least 30 days following a sub-Tenon injection.
- ocular pharmacokinetics
- rabbit eye
- sub-Tenon injection
- triamcinolone acetonide
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Funding National Natural Science Foundation of China, Grant No.30870631; 2. Qianjiang Talents Grant, No.2008R10041.
Competing interests None.
Ethics approval Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.