In order to apply cellulose acetate phthalate (CAP)-polyethylene glycol 4000 (PEG) matrix to the oral sustained-release dosage form, CAP-PEG matrix granules including nifedipine (NF) were prepared by the fusion method. Oral administration of these matrix granules to rabbits resulted in sustained-release characteristics. From the results of the pharmacokinetic study, it was considered that the plasma concentration-time course of NF after oral administration of these matrix granules follows a one-compartment model with instantaneous release and two consecutive first-order input steps. It appeared that in CAP-PEG matrix granules, PEG partly acts as a fast-release compartment and enhances the bioavailability of NF, and CAP controls the release rate of the PEG-entrapped NF. The CAP-PEG matrix appeared to be a suitable carrier of the oral drug-delivery preparation offering sustained-release.
