Abstract: Indolizine derivatives represented by the general formula: ##STR1## wherein R represents a straight- or branched-chain alkyl radical having from 1 to 8 carbon atoms, or a phenyl group non-substituted or bearing one or two substituents, which may be the same or different, selected from halogen atoms, for example fluorine, chlorine and bromine and from lower alkyl and alkoxy groups, for example methyl and methoxy and X.sub.1, X.sub.2 and X.sub.3, which may be the same or different, each represent hydrogen, chlorine, bromine or methoxy with the proviso that when they are identical X.sub.1, X.sub.2 and X.sub.3 are not simultaneously hydrogen.They possess an inhibitory activity with respect to the action of xanthine oxidase and of adenosine deaminase as well as an uricosuric action and can be used in the treatment of physiological disturbances consequent upon an excess of uric acid, upon disorders of the immunization system and as antiparasitic agents.