The paper studies the coupling reaction by covalent bonding of acetylamino-2-sulfamoyl-1,3,4-thiodiazole (AcAA) on the poly(acrylic acid-costyrene) copolymer (PAcA-S) in homogeneous system, in the presence of dicyclohexylcarbodiimide (DCC) as activator. The influence of some factors on coupling efficiency (the drug/support ratio, time, volume of solvent), as well as the mathematical model correlating the amount of coupled drug with these parameters is established. Maximum amounts of drug (28%) are chemically bound when employing maximum values of the parameters mentioned (i.e., AcAA/PAcA-S ratio = 2 mole/mole; time = 50 h; THF volume = 60 ml). Physicochemical and spectral analyses evidence the existence of some chemical bonds of the -CO-NH-SO2-type between the macromolecular support and the drug. In vivo tests have demonstrated the gradual hydrolysis of the chemical bonds as well as the release of the drug, due to the diuretic effect produced.