Mô tả thuốc bền vững-RELEASE hệ thống phân phối của Microdialysis hệ thống phân phối thuốc ban đầu được phát triển để giám sát các hợp chất nội sinh trong hệ thống thần kinh trung ương và bao gồm một màng bán thấm, thông qua đó các phân tử nhỏ có thể khuếch tán mà không có bất kỳ chuyển chất lỏng (47). | 216 Cahill and Jaffe IMPLANTED MICRODIALYSIS PROBES AS SUSTAINED-RELEASE DRUG DELIVERY SYSTEMS Description of Drug Delivery System Microdialysis was originally developed to monitor endogenous compounds in the central nervous system and consists of a semipermeable membrane through which small molecules can diffuse without any fluid transfer 47 . The microdialysis probe typically consists of an episcleral fixation plate a guide tube and a dialysis membrane made of a polycarbonate-polyether copolymer or polyamide Fig. 11 48 . The probe is inserted 4-6 mm behind the limbus through a opening and sutured to the eye with the tip of the probe containing the dialysis membrane directed as much as possible into the central vitreous. In previous animal studies connecting tubes from the probe were passed under the skin of the forehead and out between the animals ears. Microdialysis probes can both deliver substances into the vitreous and remove endogenous molecules to allow analysis of the intravitreal environment 48 49 . The main advantage of the microdialysis probe is that the amount of administered drug can be altered at anytime. This is in contrast to an implanted nondegrad-able sustained-release device which delivers the whole dose of drug at a predetermined rate unless it is removed. Furthermore microdialysis probes deliver the drug without changing the intraocular volume and can provide information about the intravitreal environment. The main potential disadvantage of the microdialysis probe is that permanent access to the vitreous cavity increases the risk of intraocular infections. However no cases of endophthalmitis were reported in previous animal studies. The microdialysis experiments also required that the connecting tubes remain in place for as long as the probes were in use which would not be practical in humans. s Ch R Figure 11 Semidiagrammatic representation of the microdialysis probe in the rabbit eye. The episcleral fixation plate F of the probe .
