Formulation and evaluation of hydrophilic matrix tablets of diltiazem using factorial design based studies

Prolonged release diltazem tablets were prepared using three grades of hydr oxypropylmethyl cellulose (HPMC) according to a 3(2) factorial design. The effects of two factors (polymer ratio and polymer type) on drug release t(5 0%) from hydrophilic matrix tablets were studied at three levels. Tablets w ere compressed by a flat-faced punch having a diameter of 11 mm using a hyd raulic press at 200 kg/cm(2). The in vitro release of diltiazem from tablet s was determined according to the USP 23 paddle method in different media ( pH 1.2, 4.0, 7.4) at 75 rpm and 37 degrees C. The effect of various excipie nts (lactose, mannitol and calcium dihydrogen phosphate) on the in vitro re lease of diltiazem has also been investigated. The releases of diltiazem fr om tablets which contained lactose and mannitol was greater than from formu lations which contained calcium dihydrogen phosphate. Topographic release p rofiles show that the release of diltiazem decreased as DH increased. The b est formulation (F14) contained lactose as a diluent. The F14 formulation s howed compared with two commercial products a prolonged release profile whe reas the commercial products released 92% and 98%, respectively, during 4 h . All the formulations except F13 which contains mannitol showed Q --> root t kinetics. The most appropriate polymer HPMC K4M with a 1:0.5 ratio has b een found by factorial design. The polymer ratio was effective on the relea se of diltiazem from hydrophilic tablets (p < 0.05).