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A new oral sustained drug delivery system (DDS) involving a combination of inorganic mesoporous material (CMK-5) and organic polymer poly dimethyl diallyl ammonium (PDDA) was established to determine its general suitability for use with poorly water soluble drugs. Nimodipine, carvedilol and fenofibrate, three different drugs with acidic or alkaline properties, were selected as model drugs and loaded into carriers. The physicochemical properties of the drug carriers were systematically studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption. The structural body changes of the composites in release medium, with or without additional salts, were also studied using particle sizing systems, nitrogen adsorption and zeta potential measurement in order to investigate the sustained release mechanism of the drugs. The results obtained showed that sustained release of drug from the designed DDS was mainly due to the blockage effect arising from the strong swelling of the coated polymers when in contact with release medium. Additional salts, when they reached a certain level, allowed a dramatic burst release. We believe that our designed sustained DDS provide a new option for water insoluble drugs and can be considered as fundamental for those more sophisticated DDS increasingly required in modern medical treatments.