INSULIN AND C-PEPTIDE LEVELS FOLLOWING ORAL-ADMINISTRATION OF INSULIN IN INTESTINAL-ENZYME PROTECTED CAPSULES

1. Crystalline beef insulin was administered orally in capsules composed of a methacrylic acid copolymer which prevented breakdown of the insulin by enteric and pancreatic peptidases. 2. In studies performed in 3 individuals blood was sampled before oral ingestion of the insulin (40-144 units), and at 15 or 30 min intervals thereafter for 5.5 hr for measurement of immunoreactive insulin and C-peptide concentrations. 3. Following the administration of oral insulin, plasma immunoreactive insulin concentrations became elevated 4-5 hr after ingestion. 4. The rise in plasma insulin concentrations was associated with a corresponding fall in the concentration of C-peptide. 5. The data suggest that this preparation of oral insulin can produce significant enteric absorption of the peptide, and that further investigation of agents that facilitate insulin absorption from the gut might render the use of methacrylic acid copolymer coated capsules a physiologically sound and a commercially feasible method of oral insulin administration.