Extended release capsules provides prolonged periods of drug in plasma levels there by reduce dosing frequency and improve patient compliance. Acetazolamide is a carbonic anhydrase inhibitor used in the treatment and management of cardiac oedema, glaucoma etc. Acetazolamide ER capsules provide prolonged action to inhibit aqueous humor secretion for 18 to 24 hours after each dose, whereas conventional tablets act for only 8 to 12 hours. Acetazolamide ER capsules were formulated using methocel K4M premium CR Hydroxy Propyl Methyl Cellulose (HPMC), methocel E10M premium CR HPMC, ethocel 10EP and ethocel 100 EP as matrixing agents. Acetazolamide capsules were prepared by direct filling method. Granules of acetazolamide were formulated by wet granulation method and filled into capsules by using hand filling capsule machine. Lubricated blend (granules) of acetazolamide was evaluated for bulk density, tapped density, % compressibility index and hausner’s ratio. Formulated capsules were evaluated for uniformity of weight, assay, in-vitro drug release studies and stability studies. Inclusion of ethocel 10EP and ethocel 100EP failed to control the release of drug, but inclusion of methocel K4M and methocel E10M the rate of drug release was controlled. The release profile was excellent and the burst release observed from the capsules containing pure drug (75.3%) at the end of first hour was overcome with methocel K4M and methocel E10M. It is concluded that the desired drug release pattern can be obtained by using methocel K4M premium CR HPMC compared to ethocel grades. The drug release followed first order kinetics and controlled by diffusion mechanism. The drug release was affected by concentration of methocel K4M premium CR HPMC.
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