Biological half-life#First-order elimination

The elimination kinetics describes the change in the excretion of a substance ( drug) in the body over time.

0-order elimination kinetics

Syn non- linear kinetics, dose-independent kinetics, capacity- limited kinetics, non- standard kinetics

A constant amount of a drug is eliminated per unit time. This means that the concentration of waste per unit time is constant and therefore independent of the plasma concentration at the moment existing. A classic example is the elimination of ethanol in the human body.

1st order elimination kinetics

Syn -linear kinetics, dose-dependent kinetics, not capacity limited kinetics, usual kinetics

The concentration of waste per unit time is not constant but is proportional to the present moment in the plasma concentration, so it is a linear function of plasma concentration. The fact that per unit time is a constant proportion of the plasma concentration is excreted, the plasma concentration initially increases rapidly with decreasing concentration and more slowly. This will be described by an exponential function. Most drugs follow a first -order elimination kinetics.

Swell

• Klaus Aktories, Ulrich Förstermann, Franz Hofmann, Wolfgang Forth: General and special pharmacology and toxicology. Urban & Fischer Elsevier, November 2004, ISBN 3-437-42521-8

• Pharmacology