By E. J. Mundell
CHICAGO (Reuters Health) – An oral insulin delivery system appears to have strong potential, according to researchers here at the 222nd national meeting of the American Chemical Society.
The new delivery method, consisting of acrylic-based copolymers with a gel-like consistency, prevents metabolism of insulin until it reaches the small intestine, investigators told conference participants on Sunday. The delivery system has low reactivity in the low pH of the stomach, but has a higher swelling ratio in the higher pH of the small intestine.
Lead investigator Aaron C. Foss of Purdue University, West Lafayette, Illinois, reported that the oral insulin delivery system has "worked beautifully" in laboratory experiments mimicking that environment.
So far, effective methods of delivering insulin to the bloodstream in pill form have largely failed because the hormone is broken down as it passes through the stomach, Dr. Foss noted.
In an interview with Reuters Health, Purdue co-researcher Dr. Nicholas A. Peppas explained that the specially designed acrylic polymer mixed with insulin allows the hormone to successfully pass through the stomach largely unharmed, reaching the small intestine, where its polymer coating reacts with the intestinal environment to release what Dr. Peppas described as "long chains that act as 'anchors,'" helping insulin adhere to the intestinal wall.
The polymer helps create a "temporary opening of the tight junctions" between cells lining the small intestine, allowing passage of insulin into the bloodstream.
In vitro studies and in studies conducted in rats and dogs, the polymer allowed about 16% of insulin to be delivered to the blood. This is a major advance over the 0.1% delivery rate of previous oral insulin delivery methods, the Purdue researchers noted.
Still, improvements are needed before the technique can hope to rival the effectiveness of injections, Dr. Peppas cautioned. "Additional animal studies with larger animals will have to be done, followed by clinical studies. Meanwhile, we are also improving the formulation."
According to a Purdue statement, the method, if successful, "could bring insulin pills and other products to market within a decade."