The invention provides formulations for oral delivery of a therapeutic agent wherein the formulation comprises a kappa opioid receptor agonist and an absorption enhancer, the absorption enhancer includes a medium chain fatty acid or a salt of a medium chain fatty acid； and a medium chain fatty acid glyceride. The kappa opioid receptor agonist may be embedded in an oligosaccharide, such as trehalose. Also provided are capsules containing the oral formulations of the kappa opioid receptor agonists and the absorption enhancer of the invention and methods use of these formulations for the prophylaxis and treatment of variety of kappa opioid receptor-associated diseases and conditions such as pain, pruritus and inflammation； the method comprising administering to the mammal the formulation comprising the kappa opioid receptor agonist and an absorption enhancer.
