Effect of daily loperamide administration on gastrointestinal myoelectric activity

The objective of this study was to determine the effect of daily administration of loperamide on gastrointestinal myoelectric activity. Six dogs were randomly administered three regimens–placebo, low dose loperamide (0.10–0.15 mg/kg/day, p.o.), and high dose loperamide (0.30–0.36 mg/kg/day, p.o.)–for one week each. Using surgically implanted bipolar electrodes, gastrointestinal myoelectric activity was recorded on at least 2 fed and 2 fasted experimental days for each regimen. In the fasted state, low dose loperamide decreased MMC cycle length, initiated intestinal amyogenesia in 40% of experiments, but did not induce vomiting. High-dose loperamide in the fasted state did not change MMC cycle length, but induced vomiting in 50% of experiments and initiated intestinal amyogenesia in 43% of experiments. The rate of occurrence of the myoelectric carrelates of giant migrating contractions (GMCs) and retrograde giant contractions (RGCs) increased with loperamide administration at both doses, as did the rate of occurrence of fed state MMCs. We conclude that daily oral administration of loperamide results in: (1) a dose-dependent effect on MMC cycle length; (2) intestinal amyogenesia; (3) an increase in frequency of vomiting at higher doses; and (4) an increase in incidence of GMCs and RGCs.