Systemic Delivery of Insulin through Eyes to Lower the Glucose Concentration

ABSTRACT An attempt has been made in this study to develop a simple, economical and painless method for the delivery of insulin systeraically without using parenteral routes. Insulin was shown to be absorbed effectively into systemic circulation through the eyes. With 0.125% (0.031 mg/25 ul), 1% (0.25 mg/25 ul), and 5% (1.25 mg/25 ul) insulin instilled topically into the eyes, systemic blood concentrations of 1.3 ng/ml, 9 ng/ml, and 24 ng/ml, respectively, could be attained. When 25 ul of 1%, 2% and 5% insulin plus 1% saponin solution were instilled into eyes they reached 63 ng/ml, 89 ng/ml and 195 ng/ml, respectively in the systemic circulation. These results indicate that the systemic absorption of 1% insulin through the eyes can be enhanced at least 7-fold when 1% of the surfactant, saponin, was added to the solution. However, the insulin absorption was not affected by aminopeptidase inhibition nor by the change of pH in the range of 5 to 8. Most importantly, the blood glucose was reduced concomitantly...