This invention provides a method of treating pain in a mammal that includes administering to a mammal in need of such treatment a pain treating effective amount of a compound of the formula (I): where R1 is H, alkyl or phenylalkyl; R2 is H, alkyl, alkenyl or phenylalkyl; or R1 and R2 taken together as Z are —CH2C—H2—, —CH2C(R6)(R7)CH2— or —CH2C(R8)(R9)—C(R10)(R11)CH2—, where R6, R8 and R10 are, independently, H, alkyl or hydroxyl and R7, R9 and R11 are, independently, H or alkyl; A is alkylene or alkenylene; X is CO2R3, P(O)(OR4)(OR5), 3,5-dioxo-1,2,4-oxadiazolidin-2-yl or 5-tetrazolyl in which R3, R4 and R5 are, independently, H or alkyl, or a pharmaceutically acceptable salt thereof. The present invention also provides pharmaceutical compositions for treating pain containing a pain treating effective amount of the compound of formula (I).
[[2-(amino-3,4-dioxo-1-cyclobuten-1-yl)amino]alkyl]-acid derivatives for the treatment of pain