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D.H. Geroski, D. Ghate, B. McCarey, W. Brooks, H.F. Edelhauser; Pharmakokinetics of Intraocular Drug Delivery by the Posterior Sub–Tenon’s Injection . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5113.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the pharmacokinetics of the posterior subtenon injection (PST).
Sodium fluorescein concentrations, 2.5mg in 0.1ml (NaF1) and 2.5mg in 0.5ml (NaF5) were injected in NZW rabbits(n=29) by PST, retrobulbar–RB and intravenous–IV routes. NaF levels in eye tissues were measured non–invasively by fluorophotometry at 5 minutes, 15 minutes, hourly for 5 hours. The NaF level in the contralateral retina was used as a measure of the systemic drug levels.
After PST with NaF1 and NaF2 peak drug levels (µg/ml) were respectively 0.8±0.6 and 1.4±0.3 in choroid/retina ; 0.3±0.2 and 0.4±0.3 in vitreous; 0.2±0.3 and 0.5±0.2 in the cornea/tear film. The peak fluorescein levels with NaF5 compared to NaF1 were 2 times greater in the retina and cornea; 1.3 times in the vitreous and equal in the retina of the contralateral control eye. The fluorescein levels in the retina were greater than 0.5µg /ml for 24 hours with the PST–NaF5, 3 hours with the PST–NaF1 and 1 hour with the RB–NaF1 and IV–NaF1 injections. With NaF1, the maximum fluorescein concentrations (µg/ml) in the retina after the PST were 0.8±0.6 l (at 3.5 hours); after the RB were 0.9±1.0 (at 1 hour) and after the IV were 0.8±.0.4 (at 15 minutes). Thus, the maximum fluorescein concentrations in the retina after PST, RB and IV injections were the same. The fluorescein levels in the retina (µg/ml) of the contralateral control eye with RB(0.3±0.2) and IV(0.8±.0.4) injections were 7 and 20 times greater than that of the PST(0.04±0.01) injection.
Higher volume of the PST injection with the same amount of drug results in larger drug peaks in the choroid/retina for a longer duration. Peak drug levels with PST, RB and IV route are the same but the PST has sustained drug release with lower systemic levels.
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