The object of the present application is to provide an effective analgesic agent for prophylaxis or treatment of various pain disorders. In particular, the present application provides an analgesic agent containing at least one trans-2-decenoic acid deriviate represented by the formula (I): [wherein, Y represents -O-, -NR- or -S-, R represents a hydrogen atom, an alkyl group or an dialkylamino group, and W represents a substitutent such as a dialkylaminoalkyl group and the like.] and a pharmaceutically acceptable salt thereof as the active ingredient. Thus, the analgesic agent of the present application which contains the above compound as the active ingredient is an excellently useful therapeutical agent for various pain disorders, for example, the agent for prophylaxis or treatment of pains caused by osteoarthritises such as osteoarthritis of the knee, osteoarthritis of the hip and the like.本發明的目的在於提供對種種的疼痛疾患的預防或治療上有效的鎮痛劑。本發明提供的鎮痛劑含有一般式(1)表示的反式-2-癸烯酸衍生物及其在藥學上可容許的鹽的至少一種為有效成分。(式中，Y表示-O-，NR-或-S-，R表示氫原子，烷基或二烷胺基等，W表示二烷胺基烷基等的取代基。)將該化合物做為有效成分的本發明鎮痛劑做為對種種的疼痛疾患治療劑，例如，變形性膝關節炎及變形性股關節炎等的變形性關節炎等引起的疼痛預防劑或治療劑的有用性高。
