Surface treatment of dimenhydrinate crystals

Dimenhydrinate is a heat-sensitive antihistamine with a low melting point. The heat-sensitive feature is of importance if direct compression is used. Direct measurement of the heat originating in the texture of tablets during compression is very difficult. Thermoanalytical methods were used as indir ect methods to describe the changes in material properties at high temperat ure: differential scanning calorimetry, thermomicroscopy and thermogravimet ric analysis. Film coating method is widely used in pharmaceutical technolo gy. A fluidized bed apparatus was applied to coat the crystals. The coating film forming agent was hydroxy-propyl-methylcellulose (HPMC), which is a g astric-soluble polymer. Thermoanalytical measurements reveal that dimenhydr inate crystals are sensitive to heat. Film coating method does not alter th e shape of the DSC curve of dimenhydrinate, but increases the melting point . The presence of a macromolecular film reduces the thermal conductivity, b ecause it separates the particles.