Dried Molasses as a Direct Compression Matrix for Oral Controlled Release Drug Delivery II: Release Mechanism and Characteristics of Theophylline from a Molasses-Hpmc Matrix

Natural gums and modified natural gums as sustained-release carriers

Although natural gums and their derivatives are used widely in pharmaceutical dosage forms, their use as biodegradable polymeric materials to deliver bioactive agents has been hampered by the synthetic materials. These natural polysaccharides do hold advantages over the synthetic polymers, generally because they are nontoxic, less expensive, and freely available. Natural gums can also be modified to have tailor-made materials for drug delivery systems and thus can compete with the synthetic biodegradable excipients available in the market. In this review, recent developments in the area of natural gums and their derivatives as carriers in the sustained release of drugs are explored.

Captopril floating and/or bioadhesive tablets: design and release kinetics

Two viscosity grades of hydroxypropylmethylcellulose (HPMC 4000 and 15,000 cps) and Carbopol 934P were used to prepare captopril floating tablets. In vitro dissolution was carried out in simulated gastric fluid (enzyme free) at 37 degrees C +/- 0.1 degree C using the USP apparatus 2 basket method. Compared to conventional tablets, release of captopril from these floating tablets was apparently prolonged; as a result, a 24-hr controlled-release dosage form for captopril was achieved. Drug release best fit both the Higuchi model and the Korsmeyer and Peppas equation, followed by first-order kinetics. While tablet hardness and stirring rate had no or little effect on the release kinetics, tablets hardness was found to be a determining factor with regard to the buoyancy of the tablets.

In vitro performance of floating sustained-release capsule of verapamil

Capsules filled with mixtures of verapamil, hydroxypropoxyl cellulose (HPC), and effervescent are proposed to provide floating sustained release over 10 hr. The effects of weight filled in the capsule, amount of HPC, and the addition of effervescent on the dissolution kinetics are studied. The conventional capsules were filled with different amounts and weights of the mixtures of verapamil, HPC, and effervescent. The release of verapamil from the capsules followed the Higuchi release model. However, when effervescent was added, a zero-order drug release was observed after the burst phase. The conventional capsule, when filled with active ingredients, polymers, and effervescent, can achieve a zero-order release system. Entrapped air was considered as a barrier to diffusion and matrix relaxation in drug release.