Enhanced rectal bioavailability of polypeptides using sodium 5-methoxysalicylate as an absorption promoter.

The absorption-promoting effect of sodium 5-methoxysalicylate was studied in the rat with respect to rectal delivery of pentagastrin and gastrin. Rectal bioavailability was quantitated by direct comparison of pharmacological effect with intravenous dose response. Coadministration of the absorption adjuvant greatly enhanced the rectal bioavailability of the model polypeptides. Sodium 5-methoxysalicylate, therefore, is representative of a new type of absorption promoter which appears to facilitate rectal absorption of polypeptide drug entities.