Abstract: The present invention relates to the crystalline mono mesylate monohydrate salt of N-[5-(aminosulfonyl)-4-methyl-1,3-thiazol-2-yl]-N-methyl-2-[4-(2-pyridinyl)phenyl]acetamide in a definite particle size range, particle size distribution and a specific surface area range, which has demonstrated increased long term stability and release kinetics from pharmaceutical compositions, as well as to pharmaceutical compositions containing said crystalline N-[5-(aminosulfonyl)-4-methyl-1,3-thiazol-2-yl]-N-methyl-2-[4-(2-pyridinyl)phenyl]acetamide mono mesylate monohydrate having the afore-mentioned particle size range, particle size distribution and specific surface area range.