Evaluation of retrograded starch as excipient for controlled release matrix tablets

High amylose starch (HAS) was retrograded by two different methods. The physicochemical properties of the retrograded materials were evaluated and structural changes were highlighted. Micromeritics properties were demonstrated as suitable for the compression process. Hydrophilic matrices were prepared by dry granulation of the retrograded starch. The in vitro release of diclofenac sodium (DS) in media with different pH values (1.2 and 7.4) was evaluated. The release profiles demonstrated the lowering of drug release rates in acid medium, mainly when pectin was associated to the matrix by physical mixture. In enteric medium, increased rates of drug release were observed, so that t80% occurred at approximately 60 min, while for the tablets obtained with HAS, this time was of approximately 120 min. The matrix obtained with pectin (during retrogradation and by physical mixture) enabled a more effective control over the drug release rates, so that t80% of DS was 150 min and 210 min, respectively.

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