Sodium insulin and zinc insulin ocular devices are developed for the systemic delivery of insulin. The devices consist of Gelfoam (absorbable gelatin sponge, USP) as an insulin carrier and do not contain any surfactant or absorption enhancer. Sodium insulin was dissolved in either distilled water, 30% ethanol, or 10% acetic acid for either eyedrop or device preparations. Because of its low solubility in water and aqueous ethanol solution, zinc insulin was dissolved in 10% acetic acid-water solution for eye devices preparation. Commercially available Humulin R was selected as another source of zinc insulin and was used as an eyedrop as well as one device preparation. Only 10% acetic acid solution-treated insulin devices produce significant blood glucose reduction. The dose of insulin used in this study is < 50% of that used in the reported insulin devices.
An ocular insert is developed for the controlled systemic delivery of insulin. Commercially available Gelfoam absorbable gelatin sponge, USP, is used in the fabrication of the ocular insert in the form of a matrix system. Two eyedrop formulations and 13 eye device formulations were evaluated. The efficacy of insulin ocular delivery was quantitated by monitoring the changes in its pharmacological response (i.e., blood glucose lowering). The in vivo results from devices containing 0.5 or 1.0 mg of insulin with 20 micrograms of polyoxyethylene-20-stearyl ether (Brij-78) give a substantial improvement in insulin activity and a significant prolongation in its duration compared with the eyedrops. In addition, the mean blood glucose concentration returns to nearly normal levels within 60 min after the removal of the device. Overall, the application of the Gelfoam device makes it feasible to obtain a prolonged systemic delivery of insulin within the desired therapeutic levels without the risk of hypoglycemia.
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