PURPOSE To compare the profiles of elevated intraocular pressure (IOP) after anterior and posterior subtenon injections (PSTIs) of triamcinolone.To characterize the vitreous pharmacokinetics of Jida, Tongyong, Triesence and Kenalog-40 following intravitreal injection.
METHODS One hundred thirty one patients (131 eyes) with a single anterior subtenon injection (ASTI) of triamcinolone acetonide acetate (20 mg in 0.5 mL) and 49 patients (49 eyes) with a single PSTI of triamcinolone acetonide acetate (40 mg in 0.4 mL) were studied for changes in IOP. Changes in IOP compared with the baseline and fellow eyes were analyzed for both the ASTI and PSTI groups.The particle size of each TA was determined by laser particle size analyzer. After intravitreal injection of four TA formulations, the aqueous humor was sampled and the drug analyzed.
RESULTS The study revealed that ASTI was 2.4 times more likely (95% confidence interval, 1.02-5.9) to have an IOP elevation >21 mmHg when compared with the PSTI (P = 0.0389). Twenty-one percent (28 of 131) of eyes having an IOP >21 mmHg were found in the ASTI group, while only 12% (6 of 49) were found in the PSTI group. Similarly, ASTI was 5.3 times more likely (95% confidence interval, 1.2-22.5) to have an IOP >30 mmHg compared with the PSTI (P = 0.03, one-tailed). Anterior subtenon injection had 7% (9 of 131) of eyes with IOP >30 mmHg, while only 2% (1 of 49) were present in the PSTI group. Age was negatively associated with IOP elevation (P < 0.05), and the baseline IOP was positively associated with IOP elevation (P < 0.05). The mean IOP elevation from the baseline was also found to be greater in ASTI (3.1 mmHg) than in PSTI (1.8 mmHg; P = 0.02, generalized estimating equation).Following intravitreal injection, Jida had the highest free TA level in aqueous (Cmax=63.2ng/mL, Tmax=1day), Triesence had the lowest free TA level in aqueous (Cmax=7.18ng/mL, Tmax=1day), and Kenalog-40 (Cmax=21.1ng/mL, Tmax=1day), Tongyong (Cmax=35.82ng/mL, Tmax=5days) showed TA levels between that of Jida and Triesence.
CONCLUSION An ASTI of triamcinolone acetonide may bear a higher risk of developing elevated IOP than a PSTI of triamcinolone acetonide. Subtenon or intravitreal TA induced high IOP may be in association with high level of TA in aqueous. |
