- History of constipation. The subject reported having on average, 2 or fewer spontaneous bowel movements per week that resulted in a feeling or sensation of complete evacuation, as well as the occurrence of one or more of the following for at least 6 months before the selection visit: very hard (little balls) and/or hard stools for at least a quarter of the stools; sensation of incomplete evacuation following at least a quarter of the stools; or straining at defecation at least a quarter of the time. The above criteria only applied to spontaneous bowel movements, (i.e., not preceded within a period of 24 hours by the intake of a laxative or use of an enema). A subject who never had spontaneous bowel movements was considered to be constipated and therefore eligible for the trial;