Trial Outcomes & Findings for Pregabalin on Colonic Motor and Sensory Function in Constipation Predominant Irritable Bowel Syndrome (NCT NCT01331213)

Participants were enrolled in the study between 4/2011 and 3/2012 at the Mayo Clinic in Rochester, Minnesota.

Pregabalin on Colonic Motor and Sensory Function in Constipation Predominant Irritable Bowel Syndrome

Colonic compliance is a measure of the "stiffness" of the colon, that is, what pressure was needed to reach half the maximum volume of the colon. After the barostat balloon catheter was inserted in the mid-descending or junction of the sigmoid and descending colon, the balloon was inflated. After an initial conditioning distension to 20 mm Hg, colonic compliance was measured by step-wise inflation with increments of 4 mm Hg. Colonic compliance was analyzed by a validated linear interpolation method. The pressure at half maximum volume serves as a summary of colonic compliance.

The symmetric percent reduction in baseline colonic barostat balloon volume during the first 30 minutes postprandially (PP) corrected for the preprandial (30 min) tone, (symmetric percent change= 100\*log\_e\[fasting/PP\]). A positive symmetric percent change reflects a decrease in barostat balloon volume indicating a reduction in colonic tone. (The balloon was placed in the mid-descending or junction of the sigmoid and descending colon.)

The sensory threshold for first perception of pain was measured by stepwise inflation of the balloon in increments of 4 mm Hg at 60 second intervals. The balloon was placed in the mid-descending or junction of the sigmoid and descending colon. During this assessment participants were asked to report when they had the first perception of pain. The investigator recorded the threshold pressure at which the participants reported this sensation.

The mm Hg distensions refer to the barostat balloon, which was placed in the mid-descending or junction of the sigmoid and descending colon. Pain sensation was measured by a 100 mm long Visual Analog Scale (VAS). The VAS does not have any pre-set marks between the extremes. For the pain VAS, 0 means no pain and 100 mm means extreme pain. The investigator measures the mark made by the participant in mm and records this for the value of pain.

Colonic tone is a measurement of the volume of the colon. Colonic tone was assessed by noting the changes in the balloon volume in the presence of a constant operating pressure in the balloon (in the barostat-manometric assembly placed in the colon.)

The postprandial motility index (MI)=log\_e\[number of contractions \* sum of amplitudes) + 1\] A normal fasting average motility index (MI) would be about 12. An increase in MI means an increase in the phasic contractions (in contrast to tone) which is measured as a change in volume of the barostatically-controlled balloon. (Therefore, an increase in MI means that the meal is moving more quickly through the colon.)

The sensory threshold for first perception of gas was measured by stepwise inflation of the balloon in increments of 4 mm Hg at 60 second intervals. The balloon was placed in the mid-descending or junction of the sigmoid and descending colon. During this assessment participants were asked to report when they had the first perception of gas. The investigator recorded the threshold pressure at which the participants reported this sensation.