Author reply

Abstract

We thank Drs Falavarjani and Modarres for their interest in our article.1Shen L. You Y. Sun S. et al.Intraocular and systemic pharmacokinetics of triamcinolone acetonide after a single 40-mg posterior subtenon application.Ophthalmology. 2010; 117: 2365-2371Abstract Full Text Full Text PDF PubMed Scopus (59) Google Scholar It has been suggested that choroidal blood flow, intraocular pressure, conjunctival/episcleral circulation, as well as various cell membrane transporters and pumps are influential to transscleral drug delivery.2Kim S.H. Lutz R.J. Wang N.S. Robinson M.R. Transport barriers in transscleral drug delivery for retinal diseases.Ophthalmic Res. 2007; 39: 244-254Crossref PubMed Scopus (116) Google Scholar However, a quantitative relationship has yet to be established. Inflammation may change the permeability of the sclera and disrupt the integrity of the ocular barrier, causing more drug distribution into the vitreous and the aqueous. In our study, 3 to 6 patients were used at each time point and the diseases were not clustered at any time point except for day 3 (Table 1, available at http://aaojournal.org), for which all 5 patients had proliferative diabetic retinopathy. The vitreous triamcinolone acetonide levels were lower at this time point, which cannot be explained by assumed inflammation or altered blood circulation. It is more likely the notches in the plots are from experimental variations, which are inevitable with any pharmacokinetic study. Therefore, identifying and analyzing the trends and trend changes of the study interests are important to correctly interpret any pharmacokinetic study. The question raised regarding the possible inequality of intravitreal level of triamcinolone acetonide among the different eye disease identities is valid. A population pharmacokinetic study or a study with a large sample size including a cross section of populations who have different eye diseases may shed further light on the issue. Table 1Eye Diseases Distribution over the Study Time PointsTime Point1 Hour1 Day3 Day5 Days10 Days14 Days21 Days28 DaysSample N46564443Eye diseasesMH, RRD, MH, CRVOPDR, PDR, RRD, AMD, MHRD, MHRDPDR, PDR, PDR, PDR, PDRRRD, PVR, PVR, MHRD, PVR, RRDMH, MHRD, PDR, EalesPDR, MH, PDR, MHRDBRVO, BRVO, PDR, MHPDR, ERM, MHAMD = age-related macular degeneration; BRVO = branch retinal vein occlusion; CRVO = central retinal vein occlusion; ERM = epiretinal membrane; MH = macular hole; MHRD = retinal detachment from macular hole; N = number; PDR = proliferative diabetic retinopathy; PVR = proliferative vitreoretinopathy; RRD = rhegmatogenous retinal detachment. Open table in a new tab AMD = age-related macular degeneration; BRVO = branch retinal vein occlusion; CRVO = central retinal vein occlusion; ERM = epiretinal membrane; MH = macular hole; MHRD = retinal detachment from macular hole; N = number; PDR = proliferative diabetic retinopathy; PVR = proliferative vitreoretinopathy; RRD = rhegmatogenous retinal detachment. Transscleral Diffusion of TriamcinoloneOphthalmologyVol. 118Issue 7PreviewIn the December 2010 issue, Shen et al1 reported the ocular and systemic pharmacokinetics of triamcinolone acetonide after a single subtenon injection. They obtained aqueous, vitreous, and blood samples during vitrectomy surgery at different time points after injections. However, they studied patients with different vitreoretinal diseases including macular hole, proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and vitreous hemorrhage associated with Eales' disease. Full-Text PDF