The aim of this study was to evaluate whether daily rapid intravenous administration of amino acids (IVAA) prevented the formation of biliary sludge in humans receiving long-term total parenteral nutrition (TPN). Thirty adult patients receiving TPN for more than 28 consecutive days were studied. They were randomized to receive either saline solution (placebo) intravenously (15 patients) or 6.9% branched chain amino acid (BCAA)-enriched amino acid (15 synthetic amino acids; Freamine HBC) solution given by administration rapid intravenous (15 patients). The groups were similar with respect to age, sex, diagnosis, liver function test results, amylase levels, TPN time, and time of study. All patients underwent weekly ultrasound studies. Volume and emptying studies of the gallbladder in response to the study drug were performed after 1 week. As a result, none of the patients receiving rapid IVAA had sludge, whereas 11 of the 15 patients receiving placebo had sludge (P < 0.01). Results of emptying studies showed significant contraction of the gallbladder in those in the rapid IVAA group, but not in the placebo group. Consequently, the data suggest that rapid IVAA given daily prevents TPN-induced stasis and sludge in the gallbladder. We conclude that rapid IVAA should be used as routine prophylaxis against biliary sludge and formation of gallstones in patients receiving long-term TPN.