Differential Scanning Calorimetry Study of the Ibuprofen–Nicotinamide Binary Disperse System and the Anti-Inflammatory Activity of One of Its Secondary Eutectics

Abstract

Phase equilibria in the solid disperse system ibuprofen–nicotinamide were studied by differential scanning calorimetry (DSC). It was established that a cocrystal (called ibunicamide) formed at a 1:1 mole ratio of ibuprofen and nicotinamide. Ibunicamide had a melting point of 91°C and underwent a simple eutectic reaction with each of the starting compounds ibuprofen and nicotinamide. The parameters of the invariant equilibrium points were determined for the secondary systems ibuprofen–ibunicamide (E1) and ibunicamide–nicotinamide (E2). Eutectics of these secondary systems appeared at mole ratios 74:26 (±1) with a eutectic melting point of 61°C (E1) and at 82:18 (±1) with melting point 82°C (E2) for the second eutectic composition. Experimental comparison of ibuprofen and the ibuprofen–nicotinamide (ibunicamide) eutectic system showed that the new composition reduced carrageenan-induced exudation by greater than 23 times as compared to the group of animals that were not treated with the NSAID. Also, the exudation after pretreatment with pure ibuprofen at the same dose was only halved. Thus, a new anti-inflammatory and analgesic drug based on the cocrystal of the ibuprofen–nicotinamide eutectic system (ibunicamide) was obtained and tested. The test results demonstrated that the anti-inflammatory activity of ibuprofen in the eutectic composition exceeded its activity in the pure form by greater than 10 times.