The first trial was a 24-week, open-labeled extension to a four-week double-blinded, pivotal trial that enrolled 308 patients. The second trial was a 48-week, open-labeled trial in 250 subjects, 82 of whom participated in a seven-week randomized withdrawal study period prior to the open-labeled phase of the study. The third trial was a 48-week open-labeled trial in 325 treatment-naive subjects. Subjects assessed treatment effectiveness, constipation severity, and abdominal symptoms of bloating and discomfort using a five-point scale.
Eligible subjects received oral lubiprostone 24mcg twice daily for six or 12 months, as needed. Subjects could then remain on a daily dosing schedule or stop the study drug if the perceived need decreased or ceased. Subjects could return to study drug when needed, but were to restart dosing again of lubiprostone at 24mcg twice daily.
The data showed that lubiprostone provided significant improvements in subjective assessments of symptoms and was well tolerated in patients with chronic idiopathic constipation. Statistically significant improvements in subjective assessments were seen in secondary endpoints including constipation severity, abdominal bloating and abdominal discomfort.
Lubiprostone (Amitiza) was approved by the FDA in January 2006 for treatment of chronic idiopathic constipation in adults and in May 2008 for the treatment of irritable bowel syndrome with constipation in adult women. Amitiza is co-marketed in the US by Sucampo Pharmaceuticals and Takeda Pharmaceuticals North America. All European rights to Amitiza are held by Sucampo Pharma Europe.