1) By refluxing N-cyano-N',S-dimethylisoithiourea (B) and 5-methyl-4-[(2-aminoethyl)thiomethyl imidazol (III) in acetonitrile. The latter is prepared by reacting cysteamine (A) and 5-methyl-4-(hydroxymethyl)imidazol (II) (from 5-methylimidazol (I) and formalin) in acetic acid, in hydrochloric acid or in hydrobromic acid. 2) By reaction of 5-methyl-4-[(2-aminoethyl)thiomethyl]imidazol (III) with cyanodithioimido carbonic (C) acid dimethyl ester to give the isothiourea (IV), followed by reaction with methylamine. 3) By refluxing 1-methyl-3-[2-[[(5-methylimidazol-4-yl)-methyl]thio]ethyl]-2-thiourea (metiamide) (V) and lead cyanamide. The first is prepared by reaction of 5-methyl-4-[(2-aminoethyl)thiomethyl]imidazol (III) with methyl isocyanate (D).