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K. D. Kovacs, M. T. Quirk, O. M. Ceron, P. S. Silva, R. J. Singh, H. J. Gukasyan, J. G. Arroyo; Pharmacokinetic Study of Vitreous and Serum Concentrations of Triamcinolone Acetonide After Posterior Sub-Tenon’s Injection. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2443.
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© ARVO (1962-2015); The Authors (2016-present)
To compare a theoretical pharmacokinetic model of triamcinolone acetonide (TA) after posterior sub-Tenon’s (PST) injection with serum and undiluted vitreous TA concentrations obtained at the time of pars plana vitrectomy.
This IRB-approved prospective, interventional study compared a theoretical model of TA diffusion after PST injection, constructed using diffusion coefficients from rabbit eyes, with TA levels in experimental undiluted vitreous and serum samples from 57 patients undergoing vitrectomy for macular hole or epiretinal membrane assessed via mass spectrometry and HPLC. At least five pairs of samples were collected at each of seven time points (1 day, 3 days, and 1, 2, 3, 4, and 8 weeks) after PST TA injection, with six controls who did not receive a steroid injection.
The theoretical model predicted that TA levels in systemic blood, vitreous and choroidal extracellular matrix would plateau after three days at 15 ng/mL, 227 ng/mL and 2230 ng/mL, respectively. Average vitreous levels of TA peaked at 111 ng/ml at day 1, then reached a plateau around 15-25 ng/mL. Average serum TA levels peaked at day 3 near 35 ng/mL, due largely to one sample with an elevated concentration, and ranged from 2-8 ng/mL at all other time points.
The theoretical model predicts efficient delivery of TA from the PST space to the extracellular choroidal matrix. The experimental findings demonstrated low levels of TA in the serum and higher levels in the vitreous lasting at least one month. Both assessments support trans-scleral delivery of PST TA.
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