Effect of aromatic hydrotropies on the solubility of carbamazepine part II effect of nicotinamide, sodium salts of benzoic naphthoic and nicotinic acids

ABSTRACT

The effect of nicotinamide and sodium benzoate, naphthoate and nicotinate on the solubility of carbamazepine in water was studied. The investigated hydrotropes were found to increase the solubility of carbamazepine. The solubilizing power of these hydrotropes was shown to be highly dependent on their chemical structure. The replacement of benzene ring by a naphthalene or pyridine ring enhances solubilization. Molecular interaction of carbamazepine with the investigated solubilizers was depicted via differential ultraviolet spectrophotometric measurements. Applying the continuous variation method revealed formation of 11 complex with sodium nicotinate, 21 complex with nicotinamide and sodium naphthoate and a mixture of 21 and 12 complexes with sodium benzoate. An apparent correlation seems to exist between the solubilizing power of these hydrotropic agents and the stability constant of their respective complexes. Calculating the amount of drug solubilized in free as well as complexed forms revealed that complex-formation as well as the decrease in activity coefficient of the drug are the two factors governing the hydrotropic behavior of these compounds towards carbamazepine