Solid solutions could represent a viable alternative to better understand and control structure–property relationships of drugs, in order to optimize their properties for practical applications. Lamivudine (3TC) and emtricitabine (FTC) are nucleoside analogue reverse transcriptase inhibitor antiretroviral drugs, which have similar molecular structures, differing by a single fluorine atom, which is only present in the FTC molecule. Due to these similarities in structure and molecular resemblances, lamivudine and emtricitabine are good candidates for producing a solid solution with physicochemical properties controlled by the stoichiometry. Following this hypothesis, the formation of a nonconventional solid solution was verified, whose crystalline structure is not defined by any of the individual constituents but by the one of the lamivudine hydrate with emtricitabine as a solute. The crystalline structures of two members of the solid solution were determined showing a nonuniform distribution of the solute among the independent molecules of the asymmetric unit of the lamivudine hydrate structure. Thermal analysis investigations confirmed that physicochemical properties could be controlled through the variation of the emtricitabine content.

中文翻译：

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抗逆转录病毒药物拉米夫定和恩曲他滨的新型固体溶液

固溶体可能是更好地理解和控制药物的结构-性质关系的可行替代方法，以便针对实际应用优化其性能。拉米夫定（3TC）和恩曲他滨（FTC）是核苷类似物逆转录酶抑制剂抗逆转录病毒药物，它们具有相似的分子结构，区别在于仅存在于FTC分子中的单个氟原子。由于这些结构和分子相似性的相似性，拉米夫定和恩曲他滨是生产具有化学计量控制的物理化学性质的固溶体的良好候选者。根据这个假设，验证了非常规固溶体的形成，其晶体结构不是由任何单独的成分定义的，而是由拉米夫定水合物中以恩曲他滨为溶质的一种定义的。确定固溶体的两个成员的晶体结构，显示拉米夫定水合物结构的不对称单元的独立分子之间溶质的不均匀分布。热分析研究证实，可通过改变恩曲他滨含量来控制理化性质。