Study on the release of acetazolamide from matrices containing tragacanth and acacia gums

Acetazolamide, a carbonic anhydrase inhibitor, is most efficient and beneficial in the treatment of glaucoma when used as a sustained release form. In the present work some sustained release matrices of the drug were formulated. Tragacanth and acacia gums matrices containing 500 mg of acetazolamide with ratios of gum to drug (RG/D) between 0.1-1 were formulated and the release study was conducted in buffer solution (pH=7.4) using USP dissolution apparatus I for 480 min. The drug release was affected by the kind of the gum as well as the RG/D values. In order to assess the efficiency of the gums, percent of drug dissolved up to any time was plotted against RG/D. The plot was named as gum efficiency curve which contained ascending and descending parts indicating two opposite effects of the gums on drug release i.e release increasing effect up to a certain RG/D and then at higher RG/Ds release decreasing effect. The corresponding turning points from ascending to descending part were 0.45 for tragacanth and 0.55 for acacia gum. Beyond these values both gums decreased the release with different efficiency. From release decreasing point of view tragacanth was much more efficient than acacia gum as it was evident from steeper slopes of its descending efficiency curves. The most suitable kinetic model for tragacanth release was zero order one with rate constant of 0.0007 - 0.0011 fraction/min whereas Weibull and log probability models were applicable for acacia matrices. Because of zero order kinetic as well as stronger release retardation efficiency the tragacanth matrices were superior to acacia matrices.