Formulation and Evaluation of Enteric Coated Timed-Release Press-Coated Tablets for Colon Targeting

As a new oral drug delivery system for colon targeting, enteric coated timed-release press-coated tablets were developed by coating enteric polymer on timed-release press-coated tablets composed of an outer shell by using different polymers and combination of polymers and core tablet containing diltiazem hydrochloride as a model drug. Press coated tablets with different weight ratio of HPC (EXF), Ethyl Cellulose (N22), Xanthan Gum, and Locust Bean Gum; as an outer coating shell and Starlac was used as filler binder in core tablet were examined for change in time lag and release pattern of diltiazem hydrochloride. After press coating, tablets were subjected to enteric coating using Instacoat EN Super II polymer. The drug release from enteric coated timed-release tablet start upon hydration of core tablet which depends on core composition and also on the outer shell. Enteric coated timed-release press-coated tablets were evaluated for thickness, hardness, friability, weight variation and in vitro dissolution test. The study showed different release pattern can be obtained from changing the coating composition. The results also showed that enteric coated timed release press coated tablets, comprising of a core tablet containing drug, an outer shell of different combinations of polymers and an enteric coating layer, showed acid resistance and time-released functions on in vitro dissolution study.