SOLID-STATE INTERACTIONS BETWEEN TRIMETHOPRIM AND PARABENS

Solid-state interactions between trimethoprim and the esters of 4-hydr oxybenzoic acid (parahydroxybenzoates or parabens) used for anti-micro bial preservation are investigated. The formation of a crystalline 1/1 molecular compound between trimethoprim and methyl parahydroxybenzoat e is demonstrated by differential scanning calorimetry, X-ray powder d iffraction, Fourier transform infrared spectroscopy, and solid-state C -13-NMR. Interactions between trimethoprim and 4-hydroxybenzoic acid a nd its ethyl,propyl and butyl esters were not observed. The nature of the trimethoprim and methyl parahydroxybenzoate intermolecular bonding is discussed briefly.