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Free keywords:
Local anesthetics; Bupivacaine hydrochloride; Racemate; Thermal analysis; X-ray diffraction
Abstract:
An amide-type local anesthetic drug, bupivacaine hydrochloride (BupiHCl), in the form of racemate is listed in the European and American pharmacopoeias and continues to be used in medicine. Thermal and X-ray analysis of commercial BupiHCl monohydrate was performed by differential scanning calorimetry with thermogravimetry, hot stage microscopy, and X-ray diffraction. Endothermic dehydration occurs at the temperature range of 73-130 A degrees C for DSC-TG 111 (Setaram) and at 83-150 A degrees C for DSC 404 (Netzsch). Both curves at 2 and 10 A degrees C min(-1) clearly reflect phase transformation of anhydrous Form I into II before reaching the melting point. A well-defined exothermic phase transition of BupiHCl was detected at a lower heating rate. Temperature-resolved X-ray diffraction in conjunction with DSC led to determining a similarity between the obtained thermal events. Microscopic investigation also confirmed the above-mentioned transformations.
