School of Pharmacy, University of Otago, P.O. Box 56, Dunedin, New Zealand; Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK; TeraView Ltd., St. John's Innovation Park, Cambridge CB4 0WS, UK.
Int J Pharm. 2013 Dec 5;457(2):510-20. doi: 10.1016/j.ijpharm.2013.03.053. Epub 2013 Apr 6.
Solid dosage forms are the pharmaceutical drug delivery systems of choice for oral drug delivery. These solid dosage forms are often coated to modify the physico-chemical properties of the active pharmaceutical ingredients (APIs), in particular to alter release kinetics. Since the product performance of coated dosage forms is a function of their critical coating attributes, including coating thickness, uniformity, and density, more advanced quality control techniques than weight gain are required. A recently introduced non-destructive method to quantitatively characterise coating quality is terahertz pulsed imaging (TPI). The ability of terahertz radiation to penetrate many pharmaceutical materials enables structural features of coated solid dosage forms to be probed at depth, which is not readily achievable with other established imaging techniques, e.g. near-infrared (NIR) and Raman spectroscopy. In this review TPI is introduced and various applications of the technique in pharmaceutical coating analysis are discussed. These include evaluation of coating thickness, uniformity, surface morphology, density, defects and buried structures as well as correlation between TPI measurements and drug release performance, coating process monitoring and scale up. Furthermore, challenges and limitations of the technique are discussed.
固体制剂是口服药物递送的首选药物传递系统。这些固体制剂通常经过包衣处理以改变活性药物成分 (API) 的物理化学性质，特别是改变释放动力学。由于包衣剂型的产品性能是其关键包衣属性的函数，包括涂层厚度、均匀性和密度，因此需要比增重更先进的质量控制技术。最近引入了一种非破坏性方法来定量描述涂层质量，即太赫兹脉冲成像 (TPI)。太赫兹辐射能够穿透许多药物材料，使包衣固体制剂的结构特征能够在深度上得到探测，这是其他已建立的成像技术（例如近红外 (NIR) 和拉曼光谱）不易实现的。在这篇综述中，介绍了 TPI 并讨论了该技术在药物涂层分析中的各种应用。这些应用包括评估涂层厚度、均匀性、表面形貌、密度、缺陷和埋入结构以及 TPI 测量值与药物释放性能之间的相关性、涂层过程监测和放大。此外，还讨论了该技术的挑战和局限性。
