Application of similarity factor in development of controlled-release diltiazem tablet

Controlled-release grade hydroxypropylmethylcellulose (PHMC) or xanthan gum (XG) and microcrystalline cellulose (MCC) were employed to prepare control led-release diltiazem hydrochloride tablets. The similarity factor f(2) was used for dissolution profile comparison using Herbesser 90 SR as a referen ce product. Drug release could be sustained in a predictable manner by modi fying the content of HPMC or XG. Moreover, the drug release profiles of tab lets prepared using these matric materials were not affected by pH and agit ation rate. The f(2) values showed that only one batch of tablets (of dilti azem HCl, HPMC or XG, and MCC in proportions of 3.0:3.0:4.0) was considered similar to that of the reference product, with values above 50. The unbias ed similarity factor f(2)* values were not much different from the f(2) val ues, ascribing to a small dissolution variance of the test and reference pr oducts. The amount of HPMC or XG incorporated to produce tablets with the d esired dissolution profile could be determined from the curves of f(2) vers us polymer content. Hence, the f(2) values can be applied as screening and optimization tools during development of controlled-release preparations.