Hydrotropic solubilization of nifedipine.

Nifedipine (1), a drug practically insoluble in water, has been solubilized employing sodium benzoate (2) and sodium salicylate (3) as hydrotropes. In 30% w/v 2 solution the solubility of 1 increased 85 and 76 fold at 25 +/- 1 degree C and at 37 +/- 1 degree C respectively. The corresponding increase in solubility of 1 in 30% w/v 3 solution was 135 and 107 fold respectively. To study the mechanism of hydrotropic solubilization of 1, the solution properties of 2 and 3 over a concentration range of 1 to 30% w/v were undertaken. The probable mechanism involves a complexation type of interaction at a low concentration of hydrotrope, aggregation of the hydrotropic molecules and inclusion of 1 in these aggregates at high concentration; and structural changes in water caused by hydrotropes.