Purchase this article with an account.
K. Banz, J. Rodger, S. Carroll, B. Boyd; Slow Release Formulations of Triamcinolone Acetonide (TA) for Intra-Vitreal Injection Provide Sustained TA Concentrations in a Rabbit Pharmacokinetic Model. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5808.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Triamcinolone acetonide (TA) is a commonly used, crystalline corticosteroid for the treatment of inflammatory conditions in the back of the eye, including choroidal neovascularisation secondary to age related macular degeneration (AMD). Commercial preparations of TA consist of micronised drug particles (particle size < 10 micron), resulting in rapid dissolution, which may limit the duration of therapeutic effect and hence the requirement for frequent dosing. In this study, we set out to test the hypothesis that an inclusion of a proportion of larger injectable TA particles (approximately 40 micron) would provide a longer dwell time in the vitreous than the commercial preparation, and therefore show potential as a longer acting form of IVTA.
Four groups of eight normal New Zealand White male rabbits received IVTA in one eye. . The first group received 3.02 ± 0.01 mg Kenalog® (Bristol Myers Squibb), which is 100% micronized; a second group received 4.27 ± 0.30 mg of large (38 micron) particle TA, and a third group received 3.97 ± 0.36 mg an 80:20 mixture of large and micronized TA. The experimental formulations were prepared by wet-sieving and freeze drying TA. The dose delivered was determined by HPLC-UV. Aqueous humour (AH) paracentesis was carried out at days 1, 3, 10, 21, 35, 60, 90, 120, 152, and 180. The TA concentration in each AH sample was analysed by enzyme linked immunosorbent assay (ELISA).
ELISA analysis showed that the two slow release formulations of groups 2 and 3 had a lower initial concentration than the reference formulation (2.89 ± 0.44 and 3.86 ± 0.52, respectively, versus 3.58 ± 0.40; ng/mL; mean ±SEM). By day 60, however, the reduction in TA concentration, compared to control, was slightly less for the large particle test formulation and similar for the mixture formulation, (to 0.78 ± 0.06 ng/mL for group 2 and to 0.72 ± 0.13 ng/mL for group 3, versus to 0.65 ± 0.17 ng/mL for group 1). The concentration of group 3 had fallen to undetectable levels by 3 months, of group 1 by 4 months, and of group 2 by 5 months. Histological analysis of the treated and contralateral eyes at 6 months showed no damage from any formulation.
Slow-release formulations, especially a formulation of 100% larger particle size, may provide provide effective, longer treatment intervals for edematous eye conditions.
This PDF is available to Subscribers Only