ABSTRACT:
Sustained release formulations are designed to eliminate multiple dose regimens. Multiple unit system improves patient compliances. A market survey reveals coating as significant aspects for avoiding environmental conditions and provides drugs stability. Pellets as a multiple unit dosage form provide opportunities for film coating due to uniform and small surface area. It also enhances surface area for absorption and since the drug is distributed in multiple units. The chances of dose dumping are negligible provides to film coating (SR) is properly optimized. It was envisaged to develop the pellets of diltiazen HCI and to optimize the pelletization process for variable like moisture content, binder, spheronization speed etc. In film coating curing is important where coated units are kept at temperature above glass transition temperature of polymer to promote coalescence of film and homogeneous distribution of plasticizers. This post coating storage alters microstructure of polymer and drug release is dependent on number of factors like plasticizers etc. Aqueous coating is recommended like surelease to avoid health hazards and environmental protection as after aqueous coating coalescence of film is often incomplete. Diltiazem HCI was used as a model drug to develop sustained release pellets by film coating and optimize the aqueous based surelease film coating to obtain sustained release effect. It has an extensive and highly variable hepatic first pass metabolism following oral administration having half life of 4.5 hrs and bioavailability of 36-50%. Moisture content, spheronization speed, spheronization time, load size and curing time should be 110%, 1500 rpm, 20 min., 50 gm and 24 hours respectively. At 400C, drug release was retarded whereas at 650C resulted in a faster drug release. Since curing of film leading to coalescence of droplet is important our main emphasis was to study effect of curing temperature on in vitro drug release.