"Drug Elimination is the irreversible loss of drug from the body. It occurs by the two processes of metabolism and excretion" [1]

Drugs generally leave the body in urine, in the original form or in some stage of a further raction product.

Natural biological systems, including animals such as humans have developed complex systems for removing and destroying harmful substances from the body.

The process of metabolism is generally broken into phase 1 and phase 2

P450 monoexygenase cycle[]

Is an important process in drug metabolism in animals.

3 main P450 enxymes involved in human drug metabolism are

  1. CYP1
  2. CYP2
  3. CYP3


  1. 1.0 1.1 Rang, H. P., Dale, M. M., Ritter, J. M., Flower R. J. and Henderson G., (2012b) ‘Drug elimination and pharmacokinetics’ in Pharmacology (7th edn), Edinburgh, Churchill Livingstone, pp. 115–22.