Thermodynamic proton-ligand and metal-ligand stability constants of some drugs.
The thermodynamic proton-ligand (pKa) and metal-ligand stability constants of clioquinol, clofibrate, nitrofurazone, and tetracycline with Cu2+, Zn2+, Mn2+, Mg2+, and Ca2+ have been determined at 35 degrees C in 50% ethanol-water media. An empirical pH correction for mixed-aqueous media has been applied. The metal-ligand stability constants were determined by following the Bjerrum Calvin titration technique as applied by Agrawal to mixed-aqueous solvents. The effect of the basicity of the ligand and the order of stability constants is discussed. The stability constants of the divalent metals follow the order: Cu2+ greater than Zn2+ greater than Mn2+ greater than Mg2+ greater than Ca2+ with all the drugs.
D002021:Buffers; D002614:Chelating Agents / Q000032:analysis; D004355:Drug Stability; D008024:Ligands; D008670:Metals / Q000032:analysis*; D009583:Nitrofurazone / Q000032:analysis; D011522:Protons; D013752:Tetracycline / Q000032:analysis; D013816:Thermodynamics
D002021:Buffers; D002614:Chelating Agents; D008024:Ligands; D008670:Metals; D011522:Protons; D013752:Tetracycline; D009583:Nitrofurazone