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F. E. Kane, K. E. Green, A. Weissman; A Comparison of in vitro Receptor Binding of Glucocorticoids. Invest. Ophthalmol. Vis. Sci. 2007;48(13):106.
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There is increasing interest in the use of glucocorticoids for the treatment of exudative and neovascular eye diseases. Data from clinical studies of sustained release dexamethasone (DEX, Posurdex®), immediate release triamcinolone acetonide (TA) and sustained release fluocinolone acetonide (FA, Retisert®) suggest that glucocorticoids may differ in their efficacy and safety which could be the result of differences in potency. The purpose of this study was to compare the in vitro receptor binding of FA to DEX and TA.
A human recombinant glucocorticoid cell membrane preparation was used for comparative binding assays after the method of DaHan, 1994. 3H-Dexamethasone (1 nM) was allowed to competitively bind to the receptors at 0° C. for 16 hours in the presence and absence of varying concentrations of FA, DEX or TA (n= 2 at each concentration). The reaction was terminated by rapid filtration through glass fiber filters. Specific radioactivity trapped on the filters was determined by liquid scintillation photometry.
The Ki values for all three glucocorticoids demonstrated they had approximately similar potencies at the human glucocorticoid receptor
In view of the very similar affinities of FA and TA for the human glucocorticoid receptor, differences in efficacy are likely to be due more to pharmacokinetic rather than pharmacodynamics differences. DEX appears to be slightly less potent based on receptor binding. The relevance of these findings will be discussed.
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