Delivery of systemic regular insulin via the ocular route in dogs

Regular porcine insulin was administered as eye drops to eight healthy, euglycemic dogs. Insulin was applied alone and in combination with six different permeation enhancers. Serum glucose and insulin were monitored for four hours following the eye drops. Significant changes in serum glucose and/or insulin occurred when the insulin was administered with 0.5% saponin, 0.5% and 1% BL-9, 0.5% and 1% dodecylmaltoside, and 0.5% and 1% tetradecylmaltoside. Insulin delivered alone and in the presence of 0.5% Brij-78 and 0.5% fusidic acid did not significantly alter glucose and/or insulin concentrations. Solutions containing 0.5% saponin induced signs of ocular irritation for approximately 5 minutes. Transient blinking (1-5 mins.) was encountered with solutions containing 1% BL-9, 1% dodecylmaltoside, and 1% tetradecylmaltoside. No ocular signs occurred with the administration of insulin alone or with 0.5% solutions of Brij-78, fusidic acid, BL-9, dodecylmaltoside, and tetradecylmaltoside. This study demonstrated that short-acting insulin is systemically absorbed in dogs via the ocular route when applied with certain emulsants.