Pharmacokinetic study of vitreous and serum concentrations of triamcinolone acetonide after posterior sub-tenon's injection.
OBJECTIVE
To compare a theoretical pharmacokinetic model of triamcinolone acetonide after posterior sub-Tenon's injection with experimental serum and undiluted vitreous triamcinolone acetonide concentrations obtained during pars plana vitrectomy.


METHODS
Clinical-practice, prospective, interventional case series study.


METHODS
This study compared computer-modeled triamcinolone acetonide diffusion after posterior sub-Tenon's injection with triamcinolone acetonide levels in experimental undiluted vitreous and serum samples from 57 patients undergoing vitrectomy assessed via mass spectrometry and high-pressure liquid chromatography. At least 5 pairs of samples were collected at each of 7 time points (1 day, 3 days, and 1, 2, 3, 4, and 8 weeks) after triamcinolone acetonide injection, with 6 controls without injection. Cortisol levels were measured in 31 sets of samples.


RESULTS
The theoretical model predicted that triamcinolone acetonide levels in systemic blood, vitreous, and choroidal extracellular matrix would plateau after 3 days at 15 ng/mL, 227 ng/mL and 2230 ng/mL, respectively. Experimental vitreous levels of triamcinolone peaked at 111 ng/mL at day 1, then reached a plateau in the range 15 to 25 ng/mL, while serum triamcinolone levels peaked at day 3 near 35 ng/mL and plateaued near 2 to 8 ng/mL. Serum triamcinolone and cortisol levels were inversely correlated (Spearman -0.42, P = .02).


CONCLUSIONS
The theoretical model predicts efficient delivery of triamcinolone acetonide from the posterior sub-Tenon's space to the extracellular choroidal matrix. The experimental findings demonstrate low levels of serum triamcinolone that alter systemic cortisol levels and higher vitreous levels lasting at least 1 month. Both assessments support trans-scleral delivery of posterior sub-Tenon's triamcinolone.
Beth Israel Deaconess Medical Center, Division of Ophthalmology, Boston, Massachusetts, USA.
Kyle
K
Kovacs
Sushant
S
Wagley
Matthew T
MT
Quirk
Olga M
OM
Ceron
Paolo A
PA
Silva
Ravinder J
RJ
Singh
Hovhannes J
HJ
Gukasyan
Jorge G
JG
Arroyo
D001682:Biological Availability; D002851:Chromatography, High Pressure Liquid; D003198:Computer Simulation; D005938:Glucocorticoids / Q000493:pharmacokinetics*; D006801:Humans; D006854:Hydrocortisone / Q000493:pharmacokinetics; D056965:Injections, Intraocular; D013058:Mass Spectrometry; D008962:Models, Theoretical; D058475:Tenon Capsule / Q000378:metabolism; D014222:Triamcinolone Acetonide / Q000493:pharmacokinetics*; D014821:Vitrectomy; D014822:Vitreous Body / Q000378:metabolism*
D005938:Glucocorticoids; D014222:Triamcinolone Acetonide; D006854:Hydrocortisone