Institute of Physics, Silesian University, Katowice, Poland.
J Pharm Sci. 2010 Feb;99(2):828-39. doi: 10.1002/jps.21877.
Verapamil hydrochloride (VH) is a very popular calcium channel blocker. Solubility of its crystalline form in the blood reaches only 10-20%. Thus, it seems to be very important to improve its bioavailability. In this article, we show that the preparation of the amorphous form of VH enhance its dissolution rate. In addition we performed dielectric measurements to describe molecular dynamics of this active pharmaceutical ingredient (API). Since examined sample is typical ionically conducting material, to gain information about structural relaxation we employed the dielectric modulus formalism. The temperature dependence of the structural relaxation time can be described over the entire measured range by a single Vogel-Fulcher-Tamman (VFT) equation. From the VFT fits the glass transition temperature was estimated as T(g) = 320.1 K. Below glass transition temperature one clearly visible secondary relaxation, with activation energy E(a) = 37.8 kJ/mol, was reported. Deviations of experimental data from KWW fits on high-frequency flank of alpha-peak indicate the presence of an excess wing in tested sample. Based on Kia Ngai's coupling model we identified the excess wing as true Johari-Goldstein process.
盐酸维拉帕米（VH）是一种非常流行的钙通道阻滞剂。其结晶形式在血液中的溶解度仅为 10-20%。因此，提高其生物利用度似乎非常重要。本文显示，制备 VH 的无定形形式可提高其溶解速率。此外，我们还进行了介电测量，以描述该活性药物成分（API）的分子动力学。由于所研究的样品是典型的离子导电材料，为了获得关于结构弛豫的信息，我们采用了介电模量形式。在整个测量范围内，结构弛豫时间的温度依赖性可以用单个 Vogel-Fulcher-Tamman（VFT）方程来描述。从 VFT 拟合中估计出玻璃化转变温度为 T(g) = 320.1 K。在玻璃化转变温度以下，报道了一个明显的二次松弛，其活化能 E(a) = 37.8 kJ/mol。在 alpha-峰高频侧的实验数据偏离 KWW 拟合表明，测试样品中存在过剩翼。基于 Kia Ngai 的耦合模型，我们将过剩翼鉴定为真正的 Johari-Goldstein 过程。
