Heterocyclic tetrahydro-1-alkyl-4-oxo-1H-imidazol-2-ylidene urea and phenyl esters of tetrahydro-1-alkyl-4-oxo-1H-imidazol-2-ylidene carbamic acid compounds

A compound selected from the group consisting of those represented by the following formula (I):

• ##STR9## wherein R is a lower alkyl radical;
• Z is a 2- or 4-pyridinyl, thienyl, furanyl, 6-lower alkyl-2-pyridinyl or 2-halogen-4-thienyl radical or a furanyl radical substituted with one substituent selected from the group consisting of hydroxyl, lower alkoxy, lower alkyl, halogen, nitro, NR.sup.1 R.sup.2, CONR.sup.1 R.sup.2, lower haloalkyl and CO.sub.2 R.sup.1 where R.sup.1 and R.sup.2 are independently selected from hydrogen and lower alkyl;
• or a pharmaceutically acceptable acid-addition salt thereof.