title: Mechanism of dissolution of cholesterol-calcium bilirubinate compressed discs in monooctanoin.
abstract: The dissolution of cholesterol monohydrate and calcium bilirubinate (neutral salt) mixtures in monooctanoin was investigated using the static disc method. The intrinsic dissolution rate of calcium bilirubinate was orders of magnitude (approximately 1000 fold) lower than that of cholesterol. Cholesterol release decreased as its weight fraction in the solid decreased. In model systems containing below 50% cholesterol dissolution became negligible. The release profiles deviated from the classical model for dissolution from two component mixtures. The observed dissolution profiles of both components were greater than predicted by theory. Anomalous positive curvatures in dissolution profiles suggested that calcium bilirubinate initially reduced the surface area available for cholesterol dissolution. A model, taking into account the change in surface area, was used to fit the cholesterol dissolution data. The results were consistent with the reported relationship between human gallbladder stone cholesterol content and average stone weight loss.
mesh_terms: D001663:Bilirubin / Q000032:analysis*; D002210:Caprylates; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002784:Cholesterol / Q000032:analysis*; D005989:Glycerides / Q000032:analysis*; D012995:Solubility
chemical_list: D002210:Caprylates; D005989:Glycerides; D002784:Cholesterol; D001663:Bilirubin; C025343:monooctanoin