The action of a calcium channel blocker (verapamil) on gallbladder contractions in humans

The class of calcium antagonists is constituted by pharmacological agents which inhibit the contraction evoked by extracellular calcium in depolarized smooth muscles. While the inhibiting action of calcium antagonists on the gastrointestinal motility is well documented, its action on the biliary tract has not been extensively studied, despite its potential clinical usefulness. Therefore we investigated the effect of a calcium channel blocker (verapamil) on fasting and postprandial gallbladder volume in normal subjects. Method: Twenty healthy volunteers participated in this study. The gallbladder volumes were measured using ultrasonography. After the baseline measurement was taken, the volunteers received 80 mg of verapamil (n:10) or a placebo (n:10) per oral in the morning one h before rescanning. The gallbladder was rescanned in 15 min intervals for 60 min. At the end of this period all the volunteers received a standard liquid test meal (Ensure), and then scans were performed again. Results: The administration of verapamil increased the fasting gallbladder volume to a maximum of 61.2% to 74.2% compared to the baseline (p<0.05) and of 49.1%- 62.6% compared to the placebo group (p<0.05). In the verapamil group significant changes in the postprandial gallbladder volumes were observed. The postprandial gallbladder volume increased to a maximum of 4.6%-61.2% compared to the baseline (p<0.05) in the first 30 min. Then it decreased to the baseline value. The gallbladder volume of the verapamil group was increased to a maximum of 86.8%-111.7% compared to the placebo group (p<0.05 and 0.01). Conclusion: These results demonstrated that verapamil significantly increased fasting and postprandial gallbladder volume.