Cholecystokinin is the most important stimulant of postprandial gallbladder contraction, and a regulator of gallbladder fasting tone. The aim of this study was to evaluate the effect of dexloxiglumide on isolated human gallbladder contraction induced by cholecystokinin-octapeptide and to compare this effect to that of lorglumide and amiglumide, two glutaramic acid analogs of dexloxiglumide. The negative logarithms of the antagonist dissociation constant (pK(B)) values were 7.00 +/- 0.14, 6.95 +/- 0.11, and 6.71 +/- 0.10 for lorglumide, dexloxiglumide, and amiglumide, respectively. Dexloxiglumide produced a concentration-dependent rightward shift of the cholecystokinin-octapeptide curve, without affecting its maximal response. A similar effect was obtained both with lorglumide and amiglumide. Moreover, the slopes for the three antagonists did not differ significantly from unity. These data show that the three molecules have a potent antagonistic effect, of a competitive nature, on gallbladder cholecystokinin type 1 receptors. It may be concluded that dexloxiglumide, lorglumide, and amiglumide exhibit a promising therapeutic profile for biliary colic and other gastrointestinal disorders in which CCK1 receptors play important physiological roles.