A therapeutic or prophylactic agent for functional bowel disorders comprisingas an effective ingredient a morphinan derivative having a nitrogen-containingcyclicgroup or a pharmaceutically acceptable acid addition salt thereof isdisclosed. Thetherapeutic or prophylactic agent for functional bowel disorders comprises asaneffective ingredient a morphinan derivative or a pharmaceutically acceptableacidaddition salt thereof, having a specific structure, such as N-(17-cyclopeopylmethyl-4,5.alpha.-epoxy-3,14-dihydroxy-morphinan-6.beta.-yl)-3,4,5,6-tetrahydrophthalimide tartaricacid salt (Compound 10).(see compound 10)
