Thermo-sensitive gel for prolongation of ophthalmic drug action

A new thermo-sensitive ophthalmic formulation has been developed on the basis of poly-N-isopropylacrylamide (poly-NIPAA) gel suspension. Gel particles effectively entrap the substances from aqueous solution at 20°C (hydrophilic state of a polymer) and form a thin film after contact with the surface of rabbit eye cornea when the gel becomes hydrophobic in character. In vitro time-consuming release of entrapped compounds from poly-NIPAA gel after a rise of temperature from 20°C to physiological temperature 37°C depends on the nature of the substance. The studies in vivo demonstrate that proxodolol (an β1,2α1-adrenoblocker, lowering intraocular pressure) in the form of poly-NIPAA gel suspension exhibits larger physiological effect on the intraocular pressure in comparison with the effect of the same drug in the form of traditional eye drops. Prolongation of action of physiologically active compounds in the form of thermo-sensitive gel suspension is expected to be sufficiently longer for more hydrophobic substances or formulation with higher molecular weight.