Trans-scleral diffusion of triamcinolone acetonide

Keywords: permeability coefficient; scleral passage; triamcinolone Introduction: Triamcinolone Acetonide (TA) is a corticosteroid largely used for therapy of intermediate/posterior ocular inflammations. In order to define the transscleral flux after a local administration, human scleral permeability to the TA was assessed in vitro. Materials and methods: the in vitro experiments were carried out using a Franz type vertical diffusion cell. The scleral samples were obtained from the whole globes of the Eye Bank of the Jules Gonin Eye Hospital (Lausanne, Switzerland). A solution of 20 mg/ml of TA was placed in the donor chamber of the apparatus, while a balanced salt solution filled the receptor compartment. TA concentration in the receptor chamber was measured by HPLC assay after 1, 2, 3, 4 and 7 days. The human sclera permeability coefficient (Ps) was finally calculated according to the Fick’s law expression. Results: the rate of solved TA ( SEM) in the donor solution was 10.69  1.28 g/ml. The steady state was reached after a 96-hour diffusion. 72% of the solved TA in the donor chamber was detected in the inferior compartment at the equilibrium, and the sclera permeability coefficient (Ps  SEM) was 1.47  0.17 x10-5 cm/second. Conclusions: TA crossed the human sclera. The mean amount of drug retained in the sclera increased with time. Four days were necessary to equilibrate the unidirectional flux. TA permeability coefficient was comparable to that of other corticosteroids.