Institute of Nuclear Medicine and Allied Sciences, Defence Research and Development Organization, Delhi, India.
J Drug Target. 2010 Aug;18(7):499-505. doi: 10.3109/10611860903508788.
Poor bioavailability (<1%) of drugs from conventional eye drops is mainly due to the various precorneal loss factors which include rapid tear turnover, systemic drug absorption through naso-lachrymal duct, transient residence time of the drug solution in the cul-de-sac and the relative impermeability of the drugs to corneal epithelial membrane. The present study describes the formulation and evaluation of chitosan and gellan gum based novel in-situ gel system activated by dual physiological mechanisms. Chitosan (a pH-sensitive polymer) in combination with gellan gum (an ion-activated polymer) were used as gelling agent. Timolol maleate, the drug which is frequently used for glaucoma therapy was used as model drug to check the efficacy of the formulation. The developed formulation was characterized for various in vitro parameters, for example, clarity, gelation pH, isotonicity, sterility, viscosity, transcorneal permeation profile, and ocular irritation. Ocular retention was studied by gamma scintigraphy and a significant increase in retention time was observed. The formulation was also found to be nonirritant and well tolerable. The developed system can be a viable alternative to conventional eye drops for the treatment of various ocular diseases and is suitable for clinical application.
常规眼药水的生物利用度（<1%）较差，主要是由于各种角膜前损失因素，包括快速的泪液周转率、通过鼻泪管的全身药物吸收、药物溶液在隐窝中的短暂停留时间以及药物对角膜上皮膜的相对通透性。本研究描述了基于壳聚糖和结冷胶的新型原位凝胶系统的配方和评价，该系统通过双重生理机制激活。壳聚糖（一种 pH 敏感聚合物）与结冷胶（一种离子激活聚合物）联合用作凝胶剂。马来酸噻吗洛尔，一种常用于治疗青光眼的药物被用作模型药物来检查制剂的功效。所开发的制剂的各种体外参数进行了特征描述，例如澄清度、胶凝 pH 值、等渗性、无菌性、粘度、角膜透过性曲线和眼部刺激性。通过伽马闪烁扫描法研究了眼部滞留情况，观察到滞留时间显著增加。该制剂也被发现无刺激性且耐受性良好。该系统可作为治疗各种眼部疾病的常规眼药水的可行替代品，适合临床应用。
