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K. Vehanen, M. Hornof, A. Urtti, H. Uusitalo; Parabulbar Use of Poloxamer for Controlled Drug Release . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5114. doi: https://doi.org/.
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The absorption of topically applied drug into the eye, especially to the retina, is not clinically sufficient. Intravitreal injections as well as the surgical implantation of devices releasing drugs can be used, but they are associated with certain risks. Use of polymers for the controlled drug delivery will provide an option between the eye drops and surgical methods. This study was undertaken to demonstrate the suitability of Poloxamer 407 (BASF) for parabulbar injections and controlled drug release.
Young Wistar rats were anesthetised before parabulbar injection of Poloxamer (25 % in 0.9 % NaCl with or without 0.1 % FITC–Dextran 20). Control animals received parabulbar injections of sodium hyaluronate. Rats were euthanaised with CO2 after 6, 12 and 24 hours, 3 and 7 days. Eyes were enucleated, embedded into paraffin and cut into 5 µm sections. Sections were stained for haematoxylin/eosin and immunostained for plasma fibronectin (CCBD) and tenascin using 3,3'–diaminobenzidine as a chromogen. The analysis was done using light microscopy.
The gelation temperature of the 25 % Poloxamer formulation is 19oC and the gel dissolves in six hours in vitro. In vivo the gel containing FITC–Dextran is visualized parabulbarly near the site of injection six hours and very faintly 12 hours after the injection. FITC–Dextran was totally disappeared after 24 hours. Clinical evaluation of the eyes and histological analysis do not show pathological changes during the first week after injection.
Parabulbar injection of Poloxamer will give a release of compounds like FITC–Dextran for at least 12 hours. Based on the clinical and histopathological evaluation Poloxamer seem to be avoid of local toxicity. For clinical purposes a more prolonged dissolution time would be desired.
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