造影剂基本知识.ppt

Overhead 02 Following intravascular injection, OMNIPAQUE? is distributed throughout the vascular system and into the extracellular interstitial fluid compartment (without crossing the cell membrane and without significant binding to plasma). Subsequently (and simultaneously) OMNIPAQUE? is rapidly excreted unchanged by glomerular filtration (without tubular secretion or reabsorption). These two processes can be described as a two-compartment model, and both show an exponential kinetics pattern (this means i.a. that the distribution and elimination kinetics are independent of the dose administered). Mathematical quantification of the pharmacokinetics are (conventionally) the so called half-lives. Distribution half-life is a value which is more theoretical than real (due to the fact that the CM is immediately excreted via kidneys when it reaches them with the blood stream - before it can be perfectly distributed in the extracellular compartment). This value can be calculated from extrapolating the curve of the CM blood concentration after the application, and it reflects the internal properties of the CM molecule (physiochemical properties, hydrophilicity, diffusability, protein binding, etc.) and the properties of the tissues as well. The elimination half-life is the time (e.g. radioactive decay or elimination of OMNIPAQUE? by the glomerular filtration) it takes to reach a blood concentration which is 50% of the concentration at the previous measurement. Typically elimination half life measurements will start at the point where the blood concentration reaches its maximum - which for injectables like CM is almost immediately after injection. Distribution and elimination half-lives of the non-ionic CM are very similar. Overhead 01 In this chapter we will present some results from preclinical studies with OMNIPAQUE? in comparison with other ionic and non-ionic contrast media. Such studies include both animal studies and in-vitro studies. Preclinical data consist of: