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[] = [] In order to find the half-life, we have to replace the concentration value for the initial concentration divided by 2: [] / = [] / and isolate the time: / = [] This t ½ formula indicates that the half-life for a zero order reaction depends on the initial concentration and the rate constant.
Absorption half-life 1 h, elimination half-life 12 h. Biological half-life (elimination half-life, pharmacological half-life) is the time taken for concentration of a biological substance (such as a medication) to decrease from its maximum concentration (C max) to half of C max in the blood plasma.
The use of trapezoidal rule in AUC calculation was known in literature by no later than 1975, in J.G. Wagner's Fundamentals of Clinical Pharmacokinetics. A 1977 article compares the "classical" trapezoidal method to a number of methods that take into account the typical shape of the concentration plot, caused by first-order kinetics. [8]
C 0 is the initial concentration (t = 0) k e is the elimination rate constant; The relationship between the elimination rate constant and half-life is given by the following equation: = / Because ln 2 equals 0.693, the half-life is readily calculated from the elimination rate constant.
C 0 is the initial concentration (at t=0) t 1/2 is the half-life time of the drug, which is the time needed for the plasma drug concentration to drop to its half; Therefore, the amount of drug present in the body at time t is;
Elimination half-life: The time required for the concentration of the drug to reach half of its original value. 12 h Elimination rate constant: The rate at which a drug is removed from the body.
An effective half-life of the drug will involve a decay constant that represents the sum of the biological and physical decay constants, as in the formula: = + With the decay constant it is possible to calculate the effective half-life using the formula:
The absorption rate constant K a is a value used in pharmacokinetics to describe the rate at which a drug enters into the system. It is expressed in units of time −1. [1] The K a is related to the absorption half-life (t 1/2a) per the following equation: K a = ln(2) / t 1/2a.