Pyridyl, thiazolyl and isothiazolyl alkyl bisamidines

A compound of the structure ##STR5## in which Het is a 5- or 6-membered fully unsaturated heterocycle containing at least one nitrogen atom, said heterocycle being pyridine optionally substituted by lower alkyl, trifluoromethyl, hydroxymethyl, halogen, hydroxy, lower alkoxy or amino;

• or thiazole or isothiazole which are attached at a ring carbon and which are optionally substituted by lower alkyl, trifluoromethyl, hydroxymethyl, halogen or lower alkoxy;
• Z is sulphur or methylene;
• m is 0, 1 or 2, n is 2 or 3, and m+n is 3 or 4;
• R is hydrogen or lower alkyl;
• each of X.sup.1 and X.sup.2 is sulphur, a nitromethylene group CHNO.sub.2, or an imino group NY, where Y is hydrogen, hydroxy, lower alkyl, cyano or carbamoyl CONH.sub.2 ;
• and
• q is from 2 to 12;
• in the form of the free base or its pharmaceutically-acceptable acid addition salts.