This invention relates to methods of preserving the integrity of peptides in the gut. In particular it concerns the use of certain compounds as inhibitors of gut proteases. Compounds identified as having gut protease inhibitory activity are biguanides, certain bile acids and pharmaceutically acceptable salts of these compounds. This activity makes these compounds useful for co-administration with prophylactic or therapeutic peptides. This invention relates to methods of inhibiting gut proteases and peptide formulations comprising these gut protease inhibitor.
