[The Cytocrome P450 as viewed from clinical practice]

The cytochrome P450 is an enzymatic system involved in the oxidative metabolism of a large number of drugs. Most clinically significant pharmacokinetic interactions are related to alterations in drug metabolism, in which the cytochrome P450 is implicated. The present article describes the structure and functioning of this enzymatic system and the mechanisms involved in metabolic interactions. Two important aspects related to this complex system are underlined: the genetic polymorphism and the influence of the environment in the activity of the enzymes. Finally, the importance of the P450 system is analyzed from the point of view of clinical practice.