Fitzpatrick Dara, Corish John
School of Chemistry, Trinity College, University of Dublin, Dublin, Ireland.
Int J Pharm. 2005 Sep 14;301(1-2):226-36. doi: 10.1016/j.ijpharm.2005.05.040.
Liquid crystalline gels (LCG) offer the formulator dynamic and flexible vehicles, into which actives, enhancers and other adjuvants with a wide range of physicochemical properties can be incorporated. This is achievable because of the biphasic oil/water composition of the gel. In this paper, the suitability of an isotropic liquid crystalline gel is investigated for a range of anionic drug molecules, with particular emphasis on sodium diclofenac. Parameters, which have been investigated, include the mode of vehicle preparation, the effect of the concentration of the drug and how buffering the gel and/or the receptor medium affect the release profiles. Such profiles have been measured for the sodium salts of benzoate, salicylate and indomethacin. The passive release from the standard system was found to adhere to matrix-controlled diffusion. An increase in concentration leads to a non-linear increase in the cumulative release of sodium diclofenac from the gels. In direct contrast to the result reported for cationic salbutamol base, optimum release from the gel was achieved when neither the receptor medium nor the aqueous phase of the gel was buffered. The percentages released of the sodium salts of benzoate, salicylate and indomethacin, after 24 h, were determined to be 25, 26 and 19%, respectively, and these are significantly greater than the release of sodium diclofenac. This suggests that diclofenac undergoes ion-pairing or complexation within the gel, which inhibits its diffusion from the vehicle. Future papers will report on the incorporation of enhancers and the effects of iontophoresis on the release profiles of drugs from these gels, and ultimately on the transdermal transport of drugs from these vehicles across human and porcine skin.
液晶凝胶（LCG）为配方设计师提供了动态且灵活的载体，具有广泛物理化学性质的活性成分、增强剂和其他佐剂都可以被纳入其中。由于凝胶的双相油/水组成，这是可以实现的。在本文中，研究了一种各向同性液晶凝胶对一系列阴离子药物分子的适用性，特别强调双氯芬酸钠。已研究的参数包括载体的制备方式、药物浓度的影响以及缓冲凝胶和/或受体介质如何影响释放曲线。已测量了苯甲酸盐、水杨酸盐和吲哚美辛钠盐的此类曲线。发现标准体系的被动释放符合基质控制扩散。浓度增加导致双氯芬酸钠从凝胶中的累积释放呈非线性增加。与阳离子沙丁胺醇碱的报道结果形成直接对比的是，当受体介质和凝胶的水相都不缓冲时，从凝胶中实现了最佳释放。苯甲酸盐、水杨酸盐和吲哚美辛钠盐在24小时后的释放百分比分别确定为25%、26%和19%，这些显著高于双氯芬酸钠的释放。这表明双氯芬酸在凝胶内发生离子对形成或络合，这抑制了其从载体中的扩散。未来的论文将报道增强剂的纳入以及离子电渗疗法对这些凝胶中药物释放曲线的影响，并最终报道药物从这些载体经皮转运穿过人体和猪皮肤的情况。
