title: Dissociation constant of chlordiazepoxide in montmorillonite suspension and its pharmaceutical application for a controlled-release dosage form.
abstract: The changes in the distribution of the ionic species of a drug due to interactions with a clay surface may have important consequences in drug therapy. The binding of chlordiazepoxide (CDO) into montmorillonite clay, veegum: HV (V), surface was studied under several pH conditions. In vitro drug release behaviour from CDO-V products was investigated. Changes in the partial molar free energy of the ionic species of CDO, delta Gi (i = CDO, CDOH+) as a result of interaction with V were determined by using differential absorbance spectroscopic techniques at 260 and 310 nm. The stronger interaction between the negatively charged clay surface and the protonated species (CDOH+) relative to the parent compound is responsible for the apparent displacement of its pKa value in V suspensions from 4.64 to 5.67. In vitro drug release behaviour from CDO-V product to the simulated gastrointestinal fluids showed a controlled pattern. The in vivo results indicated a prolonged drug effect after the oral administration of drug-clay preparation.
authors.affiliation: Department of Pharmaceutics, Assiut University, Egypt.
authors.forename: A M
authors.initials: AM
authors.lastname: el-Sayed
authors.lastname: Ismael A el-M
authors.lastname: Assi A el-A
mesh_terms: D001546:Bentonite; D002707:Chlordiazepoxide / Q000008:administration & dosage / Q000737:chemistry*; D003692:Delayed-Action Preparations; D007700:Kinetics; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013535:Suspensions
chemical_list: D003692:Delayed-Action Preparations; D012996:Solutions; D013535:Suspensions; D001546:Bentonite; D002707:Chlordiazepoxide