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In order to establish a structure and property (melting and oxidative or thermal degradation, or both) relationship for a United States Pharmacopeias (USP) set of standard drugs, they were evaluated by fast scan differential scanning calorimetry. A critical problem in characterizing the endothermic melting of a drug is to determine the melting range and if a chemical melts and immediately degrades. The stability of standard drugs is based on a comparison of their thermal properties at widely varying ramp or heating rates from 10 to 100°C/min. A stable crystalline drug has an obvious melting endotherm followed by a stable baseline. An unstable crystalline drug melts and immediately degrades as viewed by a shifting melt endotherm with heating rate. The USP thermally stable standards evaluated in this study include vanillin (melt temperature, (Tm, 80.4°C), acetanilide (Tm, 114°C), acetophenetidin (Tm, 135°C), sulfanilamide (Tm, 165°C), sulfapyridine (Tm, 191°C), and caffeine (Tm, 235°C and Tsublimation, (220°C). In addition to the USP samples a number of commercial and model drugs, like benzoic acid (Tm, 122°C and Tsublimation, (120°C), lidocaine-.HCl and procaine. HCl were also examined. Their melt profiles were ranked as stable or unstable post fusion by the fast scan DSC technique and are reported.
Riga, Alan T.
Alexander, Kenneth S.