Provided are methods and compositions for enhancing the transmucosal absorption of bioactive peptides and proteins. More particularly, the invention provides compositions for enhancing the transmucosal absorption of bioactive peptides and proteins, such as exendin-4, PYY, PYY3-36, and GLP-1 and their analogs and derivatives, wherein the compositions comprise an absorption enhancing mixture of a cationic polyamino acid and a buffer that is compatible with the polyamino acid. Also provided are methods for enhancing the transmucosal absorption and bioavailability of bioactive peptides and proteins using such compositions.