The development of an oral form of insulin has been a work in progress for many years. Many companies have decided to look for an oral form of insulin as this will help patients become more compliant with insulin therapy. They would be easier to carry around and simpler and more discreet than injecting it, so patients would be able to maintain more privacy about their need to take insulin.
Many ideas are in the works from sprays to pills. The difficulty with pills is that insulin gets easily destroyed by digestive juices in the stomach and small intestines. Finding a coating for the pill that would protect it as it traveled and dissolved once it reached the stomach was the initial problem. Also, the amount of insulin that can be put in a pill is small compared to what can be delivered in a syringe.
Insulin delivered by the oral route follows the same route to the bloodstream as insulin secreted naturally by the pancreas into the portal vein. Insulin, from the pancreas or from oral delivery, reaches the liver in high concentrations (3 times more than other tissues), activating the liver to participate in blood sugar control and regulate a number of metabolic activities that can help mitigate complications of diabetes. An oral tablet insulin product would do away with the above-cited limitations of injectable insulin, and inhaled insulin, in addition to the fact that oral delivery would have high patient compliance. Below are some companies currently trying to make this delivery process possible.
Dr. Alessio Fasano of the University of Maryland reported on research that might one day allow insulin pills to work. The report in the March 1997 Journal of Clinical Investigation (pgs. 1158-1164), uses a protein called Zonula occludes toxin or Zot. With Zot, researchers were able to significantly increase insulin transport across the intestines to lower blood sugar levels to nearly normal levels in diabetic rats. Zot is derived from Vibrio cholera. This basic research has many hurdles to pass before clinical trials begin but offers an interesting approach to the problem of protein breakdown in the stomach and intestines.