Institute of Pharmaceutics and Biopharmaceutics, University of Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
Int J Pharm. 2012 Dec 15;439(1-2):289-95. doi: 10.1016/j.ijpharm.2012.09.021. Epub 2012 Sep 16.
Terahertz pulsed imaging (TPI) is a recent and nondestructive technique to quantify coating thickness of pharmaceutical tablet film coatings. In this study, TPI is used for the first time to quantify the progress of an active coating process. The dosage form consisted of a push-pull osmotic system comprising a two-layer tablet core with a functional film coating and a laser drilled hole. On top of this system an active coating was applied. The coating thickness data acquired by TPI and optical microscopy was compared to the quantification of the active pharmaceutical ingredient (API) via HPLC. Good correlation of TPI and HPLC data was shown for coating thicknesses up to 500 μm. Due to the special structure of the dosage form, the TPI detection limit of 38 μm layer thickness was circumvented by analysing the coating thickness of active coating and functional subcoat in one. Therefore it was possible to monitor the active coating process from the very beginning of the process. Optical microscopy was no suitable reference technique for TPI thickness measurements. The active coating showed deformation artefacts during sample preparation, which biased the subsequent thickness measurements.
太赫兹脉冲成像（TPI）是一种最近的、非破坏性技术，用于定量药物片剂薄膜包衣的涂层厚度。在这项研究中，TPI 首次被用于定量活性包衣过程的进展。该剂型由推拉渗透系统组成，该系统由两层片剂芯组成，带有功能薄膜包衣和激光钻孔。在这个系统的顶部施加了活性涂层。TPI 和光学显微镜获得的涂层厚度数据与通过 HPLC 对活性药物成分（API）的定量进行了比较。对于厚度高达 500μm 的涂层，TPI 和 HPLC 数据显示出良好的相关性。由于剂型的特殊结构，通过分析活性涂层和功能次涂层的涂层厚度，可以规避 TPI 检测限为 38μm 的层厚度。因此，有可能从过程的一开始就监测活性涂层过程。光学显微镜不适合作为 TPI 厚度测量的参考技术。活性涂层在样品制备过程中显示出变形伪影，这会影响随后的厚度测量。
