A Contribution to the Glimepiride Dissociation Constant Determination

Knowledge of druglike properties, such as dissociation constants (p K a ), is of great importance in drug development and analysis. However, poor aqueous solubility often causes serious limitations in accurate determination of a drug’s p K a . In this study, the apparent dissociation constant (p K a ′ ) of the poorly soluble drug, glimepiride, has been determined by application of the spectrophotometric and solubility methods. Compared to the literature reported glimepiride p K a ′ values of 4.99 ± 0.50 and 6.2 ± 0.1, the values obtained in the present study were 8.07 ± 0.02 and 7.26 ± 0.01 determined by the spectrophotometric and solubility method, respectively. In addition, the advantages of these two methods in p K a ′ determination of glimepiride are discussed.