Isolating triamcinolone acetonide particles for intravitreal use with a porous membrane filter

Purpose: To report a new, simple, rapid method to isolate triamcinolone acetonide particles and to remove additives from its commercially available suspension (Kenacort-A) for intravitreal use. Methods: The contents of a Kenacort-A vial (40 mg triamcinolone acetonide suspended in 1.0 mL vehicle) were loaded into a syringe and passed through a porous membrane filter with 0.45-mum pores. The filter was then backflushed with distilled water to yield a vehicle-poor suspension of triamcinolone acetonide in the initial syringe. This filtration and backflush procedure was repeated four times, and each waste filtrate was subjected to high-performance liquid chromatography to identify benzyl alcohol, a preservative in the vehicle. Gel permeation chromatography was also used to determine the degree to which carboxymethylcellulose, one of the two suspending agents in the vehicle, permeated the membrane filter. Although 7.5 mg/mL high-viscosity carboxymethylcellulose hardly passed through the 0.45-mum pore filter, it passed through the 5.0-mum pore filter easily. Therefore, a 5.0-mum pore filter was used in this study. Results: By using a 0.45-mum porous membrane filter, 99.7% of the benzyl alcohol can be eliminated. By using a 5.0-mum porous membrane filter, but not by using a 0.45-mum porous membrane filter, 88.1 % of the high-viscosity carboxymethylcellulose can be eliminated. Conclusions: The filtration and backflush procedure using the 5.0-mum porous membrane filters is useful during vitrectomy to reduce the preparation time of triamcinolone acetonide suspension. Also, this method of reducing additives may be more helpful when using triamcinolone as a therapeutic agent for intravitreal depot use, because there is no washout effect when it is used in this manner.