Insulin delivery through the ocular route

The effect of insulin solution on the reduction of blood glucose concentration was studied after the administration of insulin solution through various routes-subcutaneous (SV), intravenous (IV), and ocular. Ocular administration of free insulin (400 U/mL) to normal rabbits produced no change in blood glucose level unless permeation enhancer was included in the dosing solution. Various concentrations of insulin were studied for their effectiveness on ocular administration and 10 U/kg dose was found to be optimum for ocular instillation. Among various penetration enhancers, poIyoxyethylene-9-lauryl ether (POE) in 0.8% w/w concentration exhibited better ocular compatibility and penetration-enhancing effect. The effectiveness of liposomes in aiding ocular absorption of entrapped insulin was studied in normal rabbits. Administration of insulin entrapped in positively charged liposomes composed of egg phosphatidylcholine with cholesterol and stearylamine (10: 2:1, in weight ratio) to normal rabbits produced substantial reduction in blood glucose concentration 90-120 min after the instillation of the formulation. In conclusion, it seems that administration of insulin in liposomes not only promotes the ocular absorption, but also controls and prolongs the drug action.