Studies in release behavior of diltiazem HCl from matrix tablets containing (hydroxypropyl)methyl cellulose and xanthan gum.

(Hydroxypropyl)methyl cellulose and xanthan gum were used as hydrophilic matrixing agents for preparing modified release tablets of diltiazem HCl. The amount of (Hydroxypropyl)methyl cellulose and xanthan gum exhibited significant effect on drug release from the tablets prepared by direct compression technique. Xanthan gum showed a higher ability to retard the drug release than (Hydroxypropyl)methyl cellulose. A 2(2) + 1 factorial design was adopted to study the effect of amount of (Hydroxypropyl)methyl cellulose and xanthan gum on percent drug released in first hour (Y60) and the time required for 90% drug dissolution (t90). A response surface plot is generated for investigating the effect of the independent variables on t90. The tablets containing 90 mg diltiazem HCl, 45 mg (Hydroxypropyl)methyl cellulose and 45 mg xanthan gum showed drug release upto 12 h. The value of similarity factor, f2, for the selected batch was found to be 85.1 when the dissolution study was carried out in water or simulated gastric fluid, indicating pH independent drug dissolution. The selected batch also showed a comparable release profile with a market product (f2 = 60.2). Linear relationship was observed between percent drug released and degree of swelling. The kinetics of the drug release fitted well to the Hixson-Crowell equation. It can be concluded that by using a suitable blend of (Hydroxypropyl)methyl cellulose and xanthan gum desired modified drug release can be achieved.