Influence of dissolution medium agitation on release profiles of sustained-release tablets

Reaching nearly perfect sink conditions is very important in the determinat ion of drug dissolution rates. Many times, the only factor that is taken in to consideration in achieving sink conditions is the relation between the d rug concentration and its solubility. The analytical conditions of the diss olution assay, as well as the dissolution apparatus, stirring speed, and na ture and volume of the dissolution fluid may also influence the dissolution results. The main objective of this work was to study the influence of the stirring rate conditions and of the dissolution apparatus in the diltiazem hydrochloride release from tablets. Diltiazem hydrochloride sustained-rele ase (SR) tablets were tested and the following dissolution parameters were evaluated: t(10%), t(25%), t(50%), dissolution time, mean dissolution time (MDT), and dissolution efficiency (DE) at t(120), and at t(360). To analyze the release mechanism, several release models were tested, such as Higuchi , zero order, first order, Baker-Lonsdale, Hixson-Crowell, Weibull, and Kor smeyer-Peppas. The similarities between two in vitro dissolution profiles i t-ere assessed by the similarity, factor f(2). The in vitro release kinetic s of diltiazem hydrochloride sustained-release tablets were evaluated using the USP 2 (paddle) and USP 4 (flow-through) apparatus.