Certain acids 5-alkyl-2-arylaminophenylacetic and derivatives.

A compound of formula I wherein R is methyl or ethyl; R1 is chloro or fluoro; R2 is hydrogen or fluorine; R3 is hydrogen, fluorine, chlorine, methyl, ethyl, methoxy, ethoxy or hydroxy; R4 is hydrogen or fluorine; and R5 is chloro, fluoro, trifluoromethyl or methyl; or farmaeuticamente acceptable salt thereof; esters or pharmaceutically acceptable prodrugs thereof.