NEW MATERIAL:The compound of formula I [Z1 and Z2 are =CH- or =N-; R1 is H, -Q-R5 (Q is single bond or alkylene; R5 is cycloalkyl), alkoxycarbonyl, carboxyl, hydroxyalkyl or alkyl; R2 is H, alkoxycarbonyl or carboxyl; R1 and R2 may together form alkylene; R3 and R4 are H, halogen, alkyl, alkoxy, carboxyl, cyano or group of formula II (R6 and R7 are H or alkyl); excluding the case that R1 and R2 are H, Z is =CH- and R3 and R4 are H] and its salt.

EXAMPLE: 4,4'-[(Cyclohexyl)methylene]bis(phenylguanidine) dihydrochloride.

USE: An anticoagulant.

PREPARATION: The compound of formula I can be produced e.g. by reacting a dihydrochloride of a compound of formula III with cyanamide in an organic solvent such as ethanol.