Adjuvant for promoting absorption of therapeutically active substances through the digestive tract

Claim 1

A pharmaceutical composition for absorption through the digestive tract, which comprises a therapeutically effective amount of insulin and an absorption promoting amount of an enamine derivative of the formula ##STR26## wherein ##STR27## is the residue of an organic aminocarboxylic acid or organic aminosulfonic acid having a hydrogen atom removed from the amino group thereof, the carboxyl or sulfo group in said residue being optionally in the form of an alkali metal salt or ester; wherein one of R 1 and R 2 is a carboxy or sulfo substituted alkyl of 1 to 6 carbon atoms, cycloalkyl of 5 to 6 carbon atoms, phenyl or naphthyl group and the other of R 1 and R 2 is hydrogen, lower alkyl or phenyl, R 3 is a hydrogen atom, a lower group or a lower alkoxy group, R 4 is a hydrogen atom, a lower alkyl group or a lower alkoxycarbonyl group, R 5 is a lower alkyl group, a lower alkoxy group which may optionally be substituted by hydroxyl, carboxyl or lower alkoxycarbonyl, or a lower alkylamino group which is substituted by hydroxyl, carboxyl or lower alkoxycarbonyl.