Formulation and in-vitro evaluation of sustained release matrix tablets of a selective angiotensin receptor-ii antagonist

Abstract

The present work was to formulate and evaluate sustain release matrix tablets of Losartan, an angiotensin II Receptor type 1 antagonist. Sustain release formulation are those which delivers the drug locally or systemically at a predetermined rate for a fixed period of time. The matrix tablet was prepared by direct compression method using by various concentration of chitosan and sodium alginate with combination of various release retardant polymer. The powder mixtures were subjected to various pre-compression parameters such as angle of repose, bulk density, tapped density and Carr’s index shows satisfactory result and the compressed tablets are evaluated for post-compression parameters such as weight variation, thickness, hardness, friability, drug content, in-vitro dissolution and stability studies. In this study carbopol was chosen as polymer and it was combined with chitosan and sodium alginate to explore their sustain release capability. The in-vitro release data for chitosan-carbopol and sodium alginate-carbopol based Losartan sustain released   matrix tablets are represented in table 17 and illustrated in figure 2. The in-vitro release of Losartan, from prepared matrix tablets formulations was mainly affected by dissolution medium, concentration of chitosan, concentration of sodium alginate and concentration of polymers. The in-vitro release of Losartan form prepared matrix tablets also depends on swelling behaviour of the tablets, higher the tablet swells comparative the lesser amount of drug release. The in-vitro release study was performed in 0.1 N HCl for initial first 2 hrs, and then the medium was replaced by phosphate buffer pH 6.8) and study was continued for 24 hour. The in-vitro release of Losartan was higher in first 6-7 hours in all formulations. After 1 hour, approximately 11.39%-19.54% of Losartan from chitosan-carbapol tablets, 17.10%- 22.11% from sodium alginate-carbapol, 26.22% from tablets containing only release retardant polymer has been released. Initially amount of drug release was hig her but after 6-7 hrs drug release was retarded. The stability studies were carried out for 3 months and result indicates that the selected formulations (F4 and F7) were stable.