The effect of a single oral dose of loxiglumide, a cholecystokinin antagonist, on postprandial gallbladder contraction and on gastric emptying was evaluated in humans. Following a 12-hr fasting period, two tablets of loxiglumide (400 mg each) or placebo was administered on different days, in random order and in a double-blind fashion to 10 healthy volunteers 15 min before the ingestion of a 1050-kcal standard meal. Gallbladder and antral volumes were measured by real-time ultrasonography in basal conditions and at fixed time intervals after the meal. Oral loxiglumide administration was followed by a total inhibition of the gallbladder contraction for 60 min after the end of the meal ingestion. Thereafter, up to the end of the study period, gallbladder volume was larger than that of the placebo study (at 300 min after the meal 2.7 +/- 1.6 ml after placebo and 8.2 +/- 3.5 ml after loxiglumide; P less than 0.008). No difference between placebo and loxiglumide was found in the antral volumes at any time interval (postprandial 63.5 +/- 16.5 ml after placebo and 59.4 +/- 24 ml after loxiglumide; at 300 min after the meal 20.8 +/- 13.3 ml after placebo and 18.9 +/- 9.5 ml after loxiglumide). In conclusion, a single oral dose of loxiglumide at the dose of 800 mg can inhibit postprandial gallbladder contraction without affecting gastric emptying. It would therefore appear that in man endogenous CCK, released after a solid-liquid, caloric, nutrient-balanced meal, plays a major role in the contraction of the gallbladder but does not affect gastric emptying.