Mitchell A G
J Pharm Pharmacol. 1985 Sep;37(9):601-4. doi: 10.1111/j.2042-7158.1985.tb05093.x.
Metoclopramide hydrochloride (MCPHCl.H2O) and metoclopramide base (MCP) have been studied by DSC, thermomicroscopy, X-ray diffraction and infrared spectroscopy. MCPHCl.H2O does not readily lose water of crystallization either from the solid state or from the melt, but depending on the conditions, dehydration can give rise to two anhydrous polymorphs, MCPHCl/Form I (mp 187 degrees C) and MCPHCL/Form II (mp 155 degrees C). Form I crystallizes from the melt of Form II and not by a reversible solid-solid transition. The anhydrous hydrochloride therefore shows monotropic polymorphism where Form I is the stable polymorph and Form II, a metastable polymorph. Thermal analysis of MCP shows that the base exists as two enantiotropic polymorphs. The transition of the form stable at room temperature (MCP/Form I) to the form stable at high temperatures (MCP/Form II mp 147 degrees C) occurs extremely rapidly at 125 degrees C but the reverse process requires one month at room temperature (approximately equal to 22 degrees C). It is therefore possible to compare the X-ray diffraction powder patterns and infrared spectra of MCP Forms I and II.
已通过差示扫描量热法（DSC）、热显微镜、X射线衍射和红外光谱法对盐酸甲氧氯普胺（MCPHCl.H₂O）和甲氧氯普胺碱（MCP）进行了研究。MCPHCl.H₂O无论是从固态还是熔体中都不容易失去结晶水，但根据条件不同，脱水可产生两种无水多晶型物，即MCPHCl/晶型I（熔点187℃）和MCPHCL/晶型II（熔点155℃）。晶型I由晶型II的熔体结晶而成，而非通过可逆的固-固转变形成。因此，无水盐酸盐呈现单向多晶型现象，其中晶型I是稳定的多晶型物，晶型II是亚稳多晶型物。对MCP的热分析表明，该碱以两种互变多晶型物形式存在。室温下稳定的晶型（MCP/晶型I）向高温下稳定的晶型（MCP/晶型II，熔点147℃）的转变在125℃时极其迅速地发生，但逆向过程在室温（约22℃）下需要一个月时间。因此，有可能比较MCP晶型I和晶型II的X射线衍射粉末图谱和红外光谱。
