Introduction To Pharmacokinetics
Steady State, Models And Other Terminology
FIRST ORDER ELIMINATION
In first order elimination, the rate of elimination of a drug is proportional to the drug plasma concentration: a particular proportion of the drug is eliminated over a specified time - for example 5 % every minute. (Show example).If you increase the drug plasma concentration, the amount of drug that is eliminated will increase. If you decrease the drug plasma concentration, the amount of drug that is eliminated will decrease.
If you plot a graph of drug plasma concentration against time, you obtain an exponential graph.
However, if you plot a graph of log10 drug plasma concentration against time (or concentration against time on a semilogarithmic graph), you obtain a linear graph - see across.
This is a very useful graph and can be used to find several pharmacokinetic parameters for a drug including half-life and elimination rate constant.
