Effect of loperamide and bisacodyl on intestinal transit time, fecal weight and short chain fatty acid excretion in the rat.

We analyzed the effect of drugs that modify the colonic motility on rat intestinal transit time (ITT) (measured with radiopaque markers), fecal weight (FW) and fecal concentration of short chain fatty acids (FSCFA) (assayed by gas liquid chromatography), over a four-week period. Bisacodyl was used to accelerate and Loperamide to retard the intestinal transit in rats maintained on a conventional diet. The first and 3rd week were drug-free control periods. The mean values of these periods were: ITT = 28.9h +/- 1.9 FW: 9.2 +/- 1.2 g/24 h and FSCFA = 60.6 +/- 17.9 mmol/g. After loperamide administration, we observed an increase in the mean ITT as compared to the control period (40.4 +/- 8.0h) and decrease in FW (4.8 +/- 3.6 g/24h) and in FSCFA = 32.2 +/- 5.6 mmol/g). After bisacodyl administration, we found a shorter ITT in relation to controls (24.8 +/- 2.5h), and increases in FW (27.5 +/- 3.6g/24h) and in FSCFA (108.2 +/- 39.9 mmol/g). There was a negative correlation between ITT and FW (R = 0.67 p less than 0.01) and a positive correlation between total SCFA concentration and FW (R = 0.71 p less than 0.01). The concentration of acetic, propionic and butyric acids increased with progressive increments in fecal weight, whereas concentrations of isovaleric and caproic acids decreased. The results of this study show that the FW and the FSCFA may be influenced by modifications in the intestinal transit time.