2-(4,5-dihydro-1H-imidazol-2-yl)-1,2,4,5-tetrahydropyrrolo[3,2,1 -hi]indole derivatives useful as antidiabetic agents

A method of treating diabetes in a patient, which comprises administering to said patient an effective antidiabetic amount of a compound of the general formula (I) ##STR3## in which R is hydrogen or a linear or branched C.sub.1-4 alkyl group, and R.sub.1 and R.sub.2, which may be the same or different, are hydrogen, halogen or C.sub.1-4 alkyl, said compound being in the form of a pure enantiomer or of a mixture of enantiomers, or an addition salt thereof with a pharmaceutically acceptable acid.