Abstract
The aim of this research was to investigate the technique for preparation of coated valproic acid and sodium valproate sustained-release matrix tablets. Different diluents were tested and selected as the effective absorbent for oily valproic acid. Effect of the amount of absorbent and hydroxypropylmethylcellulose on drug release from valproic acid-sodium valproate matrix tablets prepared with wet granulation technique was evaluated in pH change system. Colloidal silicon dioxide effectively adsorbed liquid valproic acid during wet granulation and granule preparation. The amounts of colloidal silicon dioxide and hydroxypropylmethylcellulose employed in tablet formulations affected drug release from the tablets. The drug release was prominently sustained for over 12 h using hydroxypropylmethylcellulose-based hydrophilic matrix system. The mechanism of drug release through the matrix polymer was a diffusion control. The drug release profile of the developed matrix tablet was similar to Depakine Chrono®, providing the values of similarity factor (f2) and difference factor (f1) of 85.56 and 2.37, respectively. Eudragit® L 30 D-55 was used as effective subcoating material for core matrix tablets before over coating with hydroxypropylmethylcellulose film with organic base solvent. Drug release profile of coated matrix tablet was almost similar to that of Depakine Chrono®.
Highlights
The aim of this research was to investigate the technique for preparation of coated valproic acid and sodium valproate sustained-release matrix tablets
Hydroxypropylmethylcellulose (HPMC) is the major hydrophilic carrier material used for the preparation of oral controlled drug delivery systems
Valproic acid (VA) and sodium valproate (VAS) are anticonvalsants widely used for treatment of simple and complex absence seizures
Summary
Valproic acid (Lot 041101) and sodium valproate (Lot 040901E) were purchased from Hunan Xiangzhong Pharmaceutical Co., Ltd., Shaoyang Hunan, China. Talc, microcrystalline cellulose, calcium carbonate, corn starch and dibasic calcium phosphate were individually tested for VA adsorption by mixing with VA 145 mg Each of these excipients was gradually weighed for mixing with VA using mortar and pestle until VA was completely adsorbed with no liquid residue left (n=3). Wet granules were prepared by adding PVP-K 90 in isopropyl alcohol solution (3% w/w of total weight of core tablet formulation) into powder mixture, sheared by the pestle and screened through a 12-mesh sieve. Preparation of film coated matrix tablet: The VA and VAS sustained release core tablets were coated with film coater In vitro dissolution testing of VA and VAS sustained release tablets was determined using a USP apparatus II dissolution tester (model VK7010, Vankel, NJ, USA), operating at 100 rpm. Yobsi and Ycali are observed and calculated values of the i-th point, respectively, and wi is the weight that applies to the i-th point, n is number of points and p is number of parameters
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