The invention relates to guanidine derivatives of formula (I) where: A represents a chain of 3-6 carbon atoms, one of which can be replaced by —N(R′)— or —O— and R′ is H or a substituent; the ring skeleton only contains both double bonds of the thiazole component; the pharmaceutically-acceptable acid addition salts of basic compounds of formula (I), the pharmaceutically-acceptable salts of compounds of formula (I), comprising acid groups, with bases, the pharmaceutically-acceptable esters of hydroxy or carboxyl group containing compounds of formula (I) and the solvates or hydrates thereof, which exhibit a neuropeptide FF receptor antagonist effect. The above are suitable for the treatment of pain and hyperalgesia, withdrawal symptoms in alcohol, psychotropic and nicotine dependencies, for improvement or cure of said dependencies, for regulation of insulin excretion, food intake, memory functions, blood pressure, electrolyte and energy management and for treatment of urinary incontinence. The above can be produced using generally used methods and processed to give medicaments.