Enhancement of oral bioavailability of insulin in humans.

OBJECTIVE: The purpose of this study is to investigate oral absorption of 1, 2 and 3 U/kg oral insulin five test products with different particle sizes in comparison with 0.1 U/kg subcutaneous reference formulation.

METHODS: Twenty five healthy volunteers participated in five studies using a two-phase, two-sequence crossover design with washout period of one day. Mean disposition kinetics was determined by non-compartmental analysis using Kinetica program. Absorption kinetics of insulin products were then determined using SIMCYP simulator utilizing ADAM model.

RESULTS & CONCLUSIONS: Dimensional analysis results showed the superiority of formula 4:2 U/kg oral dose with 57 nm particle size over other oral formulations when compared with subcutaneous route. Optimized intestinal permeability coefficients (x10(-4)) of insulin best test and reference formulations were 0.084 and 0.179 cm/sec respectively. Total fraction of insulin dose absorbed (Fa) for the test and reference products were 3.0% and 19% respectively. Subcutaneous product exhibited higher absorption rate and extent than oral insulin. Yet that was compensated by the increase in other factors such as Fa*, Peff* and oral dose, leading to similar insulin plasma levels and similar effect on glucose infusion rates. Oral insulin bioavailability was shown promising for the development of oral insulin product.