Elimination rate constant

The elimination rate constant K is a value used in pharmacokinetics to describe the rate at which a drug is removed from the system.

It is often abbreviated K or K_e. It is equivalent to the fraction of a substance that is removed per unit time measured at any particular instant and has units of T⁻¹. This can be expressed mathematically with the differential equation

where ${\displaystyle C_{t}}$ is the blood plasma concentration of drug in the system at a given point in time ${\displaystyle t}$, ${\displaystyle dt}$ is an infinitely small change in time, and ${\displaystyle C_{t+dt}}$ is the concentration of drug in the system after the infinitely small change in time.

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