Report: in vitro dissolution studies of different brands of sustained release diclofenac sodium matrix tablet available in Bangladesh.

Commercially available national thirteen brands and three international brands of diclofenac sodium sustained release matrix tablets were studied in simulated gastric medium (pH 1.2) for 2 hours time period and simulated intestinal medium (pH 6.8) for 10 hours time period using USP reference dissolution apparatus. All the national and international brands complied with the USP in-vitro dissolution specification for drug releases in simulated gastric medium. However, four of the national brands (Code: DS-5, DS-8, DS-12, and DS-13) failed to fulfill their official requirement of 80% drug release within 8th hour in simulated intestinal medium. Drug release of those four national brands were 78.1%, 74.9%, 72.1%, and 77.8% respectively within the specified time period, however one national brand (Code: DS-2) released 83.2% drug within 6th hour in intestinal medium. Drug release profiles were analyzed for Higuchi equation, zero order, and first order to reveal the release kinetics perspective of diclofenac sodium sustained release matrix tablets. It was found that zero order release kinetics was predominant release mechanism than first order and Higuchi release kinetics for those brands (Code: DS-1, DS-3, DS-4, DS-6, DS-7, DS-9, DS-10, DS-11, DS-X, DS-Y and DS-Z) which complied with the USP in vitro dissolution specification for drug releases. On the other hand, first order release kinetics was predominant for five national substandard formulation brands (Code: DS-2, DS-5, DS-8, DS-12 and DS-13).