IMPROVING INSULIN ENTERAL ABSORPTION USING WATER-IN-OIL-IN-WATER EMULSION

The purpose of this study was to evaluate the hypoglycemic effects of water-in-oil-in-water (W/O/W) insulin emulsions containing lipoidal ab sorption enhancer after enteral administration to rats. The hypoglycem ic effects of insulin were examined using an in situ loop method in ra ts. The insulin emulsions prepared with soybean oil, triolein or trili nolein slightly but significantly decreased the serum glucose levels c ompared to the insulin solution. By addition of 3% limonene or 3% ment hol to the triolein emulsion, the hypoglycemic effect of insulin was p romoted in the ileum but not in the colon. Strong hypoglycemic effects were observed with the triolein emulsion containing 2% fatty acids su ch as oleic acid, linoleic acid and linolenic acid. The remarkable enh ancing effects occurred more predominately in the colon than in the il eum. The effect of degree of unsaturation of fatty acids was not obser ved. No tissue damage was noted by light microscopic examination of bo th regions treated with triolein emulsion, triolein emulsion containin g menthol or oleic acid. W/O/W emulsion containing unsaturated fatty a cids are able to enhance the ileal and colonic absorption of insulin w ithout tissue damage and may, therefore, be useful in dosage form in e nteral delivery system for insulin. (C) 1998 Elsevier Science B.V. All rights reserved.