Department of Chemistry and the Macromolecular Science & Engineering Program , The University of Michigan , Ann Arbor , Michigan 48109 , United States.
Mol Pharm. 2019 Feb 4;16(2):682-688. doi: 10.1021/acs.molpharmaceut.8b00972. Epub 2019 Jan 15.
Amorphous solid dispersions of pharmaceuticals often show improved solubility over crystalline forms. However, the crystallization of amorphous solid dispersions during storage, or from elevated supersaturation once dissolved, compromise the solubility advantage of delivery in the amorphous phase. To combat this phenomenon, polymer additives are often included in solid dispersions to inhibit crystallization; however, the optimal properties for polymer to stabilize against crystallization are not fully understood, and furthermore, it is not known how inhibition of precipitation from solution is related to the propensity of a polymer to inhibit crystallization from the amorphous phase. Here, polymers of varied hydrophobicity are employed as crystallization inhibitors in supersaturated solutions and amorphous solid dispersions of the BCS Class II pharmaceutical ethenzamide to investigate the chemical features of polymer that lead to long-term stability for a hydrophobic pharmaceutical. A postpolymerization functionalization strategy was employed to alter the hydrophobicity of poly( N-hydroxyethyl acrylamide) without changing physical properties such as number-average chain length. It was found that supersaturation maintenance for ethenzamide is improved by increasing the hydrophobicity of dissolved polymer in aqueous solution. Furthermore, amorphous solid dispersions of ethenzamide containing a more hydrophobic polymer showed superior stability compared to those containing a less hydrophobic polymer. This trend of increasing polymer hydrophobicity leading to improved amorphous stability is interpreted by parsing the effects of water absorption in amorphous solid dispersions using intermolecular interaction strengths derived from global structural analysis. By comparing the structure-function relationships, which dictate stability in solution and amorphous solid dispersions, the effect of hydrophobicity can be broadly understood for the design of polymers to impart stability throughout the application of amorphous solid dispersions.
药物无定形固体分散体通常表现出比结晶形式更高的溶解度。然而，在储存过程中或溶解后达到过饱和状态时，无定形固体分散体的结晶会破坏在无定形相下递送的溶解度优势。为了克服这一现象，通常在固体分散体中加入聚合物添加剂以抑制结晶；然而，对于聚合物稳定结晶的最佳性质尚未完全了解，此外，也不知道从溶液中沉淀的抑制与聚合物抑制无定形相结晶的倾向之间的关系。在这里，使用不同疏水性的聚合物作为结晶抑制剂，用于过饱和溶液和 BCS 类 II 药物乙酰胺的无定形固体分散体中，以研究导致疏水性药物长期稳定的聚合物的化学特征。采用后聚合官能化策略改变聚（N-羟乙基丙烯酰胺）的疏水性，而不改变例如数均链长等物理性质。发现增加水溶液中溶解聚合物的疏水性可提高乙酰胺的过饱和度维持。此外，含有疏水性聚合物的乙酰胺无定形固体分散体比含有疏水性较低的聚合物的无定形固体分散体具有更好的稳定性。这种增加聚合物疏水性导致改善无定形稳定性的趋势，可以通过使用源自全局结构分析的分子间相互作用强度解析无定形固体分散体中水吸收的影响来解释。通过比较决定溶液和无定形固体分散体稳定性的结构-功能关系，可以广泛理解疏水性对于在无定形固体分散体应用中赋予稳定性的聚合物设计的影响。
