藥品仿單上看到terminal half life 上google查了一下 似乎有別於一般half time的定義 但是又看不大懂(下面有三個連結) 煩請專業藥學人士指點 謝謝 http://www.netwellness.org/question.cfm/71892.htm The half life is the time it takes for the plasma concentration or the amount of drug in the body to be reduced by 50%. In the simplest model of drug elimination from the body, a drug declines at a constant rate. However, many drugs are not eliminated from the body at a constant rate. These drugs leave the body in a more complicated pattern of decline. Factors such as how widely the drug is distributed throughout the body and how easily the body is able to remove the drug from the plasma influence the rate of elimination. The rate may change over time rather than being constant. The term "terminal half life" is used for the slowest process of concentraton decrease of a drug from the body. http://www.ncbi.nlm.nih.gov/pubmed/15601438 Terminal plasma half-life is the time required to divide the plasma concentration by two after reaching pseudo-equilibrium, and not the time required to eliminate half the administered dose. When the process of absorption is not a limiting factor, half-life is a hybrid parameter controlled by plasma clearance and extent of distribution. In contrast, when the process of absorption is a limiting factor, the terminal half-life reflects rate and extent of absorption and not the elimination process (flip-flop pharmacokinetics). The terminal half-life is especially relevant to multiple dosing regimens, because it controls the degree of drug accumulation, concentration fluctuations and the time taken to reach equilibrium. http://www.alprolix.com/efficacy/half-life.html Terminal half-life is the time it takes for a drug's activity to decrease by half after the drug has been distributed throughout the body. The longer the terminal half-life, the longer factor is active in your system. --

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