A randomised controlled study of the effect of cholinesterase inhibition on colon function in patients with diabetes mellitus and constipation.

Chronic constipation in diabetes mellitus is associated with colonic motor dysfunction and is managed with laxatives. Cholinesterase inhibitors increase colonic motility. This study evaluated the effects of a cholinesterase inhibitor on gastrointestinal and colonic transit and bowel function in diabetic patients with constipation. After a 9-day baseline period, 30 patients (mean ± SEM age 50 ± 2 years) with diabetes mellitus (18 type 1, 12 type 2) and chronic constipation without defaecatory disorder were randomised to oral placebo or pyridostigmine, starting with 60 mg three times a day, increasing by 60 mg every third day up to the maximum tolerated dose or 120 mg three times a day; this dose was maintained for 7 days. Gastrointestinal and colonic transit (assessed by scintigraphy) and bowel function were evaluated at baseline and the final 3 and 7 days of treatment, respectively. Treatment effects were compared using analysis of covariance, with gender, body mass index and baseline colonic transit as covariates. 19 patients (63%) had moderate or severe autonomic dysfunction; 16 (53%) had diabetic retinopathy. 14 of 16 patients randomised to pyridostigmine tolerated 360 mg daily; two patients took 180 mg daily. Compared with placebo (mean ± SEM 1.98 ± 0.17 (baseline), 1.84 ± 0.16 (treatment)), pyridostigmine accelerated (1.96 ± 0.18 (baseline), 2.45 ± 0.2 units (treatment), p<0.01) overall colonic transit at 24 h, but not gastric emptying or small-intestinal transit. Treatment effects on stool frequency, consistency and ease of passage were significant (p ≤ 0.04). Cholinergic side effects were somewhat more common with pyridostigmine (p=0.14) than with placebo. Cholinesterase inhibition with oral pyridostigmine accelerates colonic transit and improves bowel function in diabetic patients with chronic constipation.