Feasibility of insulin eyedrops for human use.

To determine the minimum effective concentration of insulin eyedrops for human use, insulin eyedrops at 0.01%, 0.05%, and 0.25% plus 0.5% Brij-78 were instilled into rabbit eyes. Brij-78 (0.5%) eyedrops were instilled as control. It was found that very low concentrations of insulin such as 0.05% plus 0.5% Brij-78 can reduce the blood glucose effectively in rabbits. The 0.05% insulin with 0.5% Brij-78 seems to be the best choice. Assuming the human body weight is approximately 25 times that of the rabbit, the concentration of insulin to be used for human patients would be 1.25% insulin (0.05% x 25), which is equivalent to 1.25 mg insulin/75 kg body weight. Because the absorption rate of insulin eyedrops plus Brij-78 is approximately 60-70%, 1.25% insulin plus Brij-78 would easily reach the therapeutic dose of insulin by injection (0.4-0.5 mg/75 kg). These results indicate that it is feasible to use insulin eyedrops to lower the blood glucose in humans. There was no statistical difference in blood glucose levels between animals instilled with 0.5% Brij-78 alone as control and those instilled with 0.01% insulin plus 0.5% Brij-78.