Differential Scanning Calorimetry Study of Binary Antimicrobial Systems with Trimethoprim: Activity of Eutectics

Results of differential scanning calorimetry studies of phase equilibria in binary systems of a series of sulfanilamides, levofloxacin, and levomycetin in combination with trimethoprim are presented. The studied systems were found to be simple eutectics. The congruent equilibrium compositions and melting points of nine pairs of systems and results of preclinical investigations are reported. The rate of development of microbial resistance to a composition modeling a commercial combination was four times greater than the eutectic composition. The antimicrobial activity of the eutectic mixtures was from 2 to 2000 times greater than those of the individual components. The observed properties could be useful for clinical application of eutectic dispersions as antimicrobial drug delivery systems for more effective achievement of the therapeutic goals.