Comparison of different techniques for purification of triamcinolone acetonide suspension for intravitreal use.

BACKGROUND: Intravitreal triamcinolone has increasingly been used for the treatment of oedematous and neovascular diseases and purification of triamcinolone suspension may be important in order to avoid the potential toxic effects of the vehicle. The aim was to evaluate different techniques used to reduce the solvent agent benzyl alcohol (9.9 mg/ml) from a commercially prepared triamcinolone acetonide suspension.
METHODS: Different techniques were used to reduce the solvent agent benzyl alcohol: filter techniques using 0.22 mum or 5 mum pore size, and non-filter techniques using sedimentation or centrifugation. Quantification of triamcinolone acetonide and benzyl alcohol was performed by high pressure liquid chromatography (HPLC).
RESULTS: Benzyl alcohol concentration was decreased significantly in all the techniques used compared with the original commercial suspension (p<0.05), with no significant differences among them. The reduction was approximately one tenth of its original concentration. However, triamcinolone acetonide concentration differed significantly depending on the method used. Centrifugation method showed no differences versus the original commercial solution; sedimentation technique reduced the expected dose only 25%; the filter technique using a 5 mum pore size membrane reduced the expected dose to one fourth, while the filter technique using a 0.22 mum pore size membrane reduced the expected dose to 45%.
CONCLUSIONS: All the different techniques employed effectively reduced the concentration of benzyl alcohol. However, the final concentration of triamcinolone was much lower than expected using the filter techniques. The pore size membrane inversely influenced the final concentration, with part of the triamcinolone crystals probably being entrapped in the filter. Centrifugation is recommended as the best way of administering the drug.