A persistent microsphere preparation comprising a biodegradable polymer and acid (E) - [5- [2- (1- phenyl-1- (3-pyridyl) methylidenaminoxy] ethyl] -7,8-dihydronaphthalen-1-yloxy] - acetic or salts thereof.Una preparacion de microesferas persistentes que comprende un polimero biodegradable y acido (E)-[5-[2-(1- fenil-1-(3-piridil)metilidenaminoxi]etil]-7,8-dihidronaftalen-1-iloxi]-acetico o sales del mismo.