Physical parameters and biological activity of sulfonamides.

The activity coefficients "gamma" aqueous solution and the diffusion rate constants (Kd) from artificial gastric and intestinal juices were measured for eleven sulfonamides; the corresponding absorption rate constants (Ki) were then calculated. The activity coefficient was correlated with various parameters, such as the n-octanol/water and isoamyl acetate/water partition coefficients, and the absorption constant. The activity coefficient "gamma" plays an important role on the global biological activity, even if partly depending upon chemical interactions. Constant ratios (about 10%) referred to solubility of the sulfonamidic compounds in the "amorphous state" were regarded as available in blood for biological activity, regardless of the respective binding with plasma proteins.