Triamcinolone acetonide preparations: impact of crystal size on in vitro behavior

To characterize the in vitro behavior of three preparations of triamcinolone acetonide (TA).

Three preparations of TA were mixed with Balanced Salt Solution Plus: commercially available TA (Kenalog 40, Bristol-Myers Squibb, Princeton, NJ), compounded preservative-free triamcinolone acetonide (PFTA, New England Compounding Center, Framingham, MA), and triamcinolone acetonide injectable suspension (TAIS, TRIESENCE, Alcon, Inc., Fort Worth, TX). We determined the mean number of crystalline aggregates per high-power deconvolution microscopy field, largest aggregate area, and spectroscopic photometric absorption.

Preservative-free triamcinolone acetonide had larger mean number of aggregates compared with TA (time 0 P = 0.002, 10 minutes P < 0.001) and TAIS (time 0 P < 0.001, 10 minutes P = 0.003). Aggregate size varied at both 0 and 10 minutes: TAIS > TA > PFTA. Spectroscopic photometric absorption decreased in direct correlation to aggregate size over time for all three preparations.

In vitro, PFTA in Balanced Salt Solution Plus had more aggregates of smaller size than either TA or TAIS. By contrast, TAIS had much larger aggregate size than both PFTA and TA, and this increased over time. These findings correlate with the clinical observations that PFTA and TA tend to disperse throughout the vitreous, whereas TAIS tends to conglomerate and gravitate toward the most dependent portion of the eye in a globular fashion.