Trans-scleral diffusion of triamcinolone acetonide

Purpose: To assess ex vivo human scleral permeability to triamcinolone acetonide ( TA). Methods: The experiments were carried out using scleral samples and a Franz-type vertical diffusion cell. A suspension containing TA was prepared and placed in the donor chamber. The concentration of TA in the receptor chamber was measured by high-performance liquid chromatography ( HPLC) assay and expressed as a percentage relative to TA concentration dissolved in the donor chamber. Control experiments using a commercial TA suspension were performed. Results: TA (+/- SEM) dissolved in the donor suspension was 10.69 +/- 1.28 mu g/ml. The diffusion rate of TA varied from 30% after 1 day to 72% after 4 days, after which equilibrium was reached. The human scleral permeability coefficient (P-s +/- SEM) was 1.47 +/- 0.17 x 10(-5) cm/s. Conclusions: TA crossed human sclera. The mean amount of drug retained in the sclera increased with time, 4 days being necessary to equilibrate the unidirectional flux. The TA permeability coefficient was comparable to that of other corticosteroids.