";s:4:"text";s:4379:" The role of the CYP family of enzymes. It is now realized that many drug-drug interactions can be explained by alterations in the metabolic enzymes that are present in the liver and other extra-hepatic tissues. Philosophical Transactions of the Royal Society of London. The incidence of side-effects is markedly higher in the elderly and those with more severe symptoms. CYP1A1 is not significantly expressed in the liver. At the present time a number of CYP isoenzymes are expressed in each mammalian species including humans [This pedigree is indicated by, respectively, an Arabic numeral (family), a capital letter (subfamily) and another Arabic numeral (gene), e.g. Pharmacokinetic interactions involve the effect of one drug on the absorption,metabolism, excretion or protein binding of another drug. Cimetidine is bound to P450 and produces a stable cytochrome-substrate complex. This review presents a brief historical overview of the discovery and characterization of P450 enzymes extending from intermediary metabolism to the fields of drug metabolism and toxicology. CYP2D6 is potently blocked by fluoxetine, paroxetine, quinidine and ritnavir; which will cause significant and even dangerous, interactions.CYP450 3A4 metabolises, amongst others for instance, terfenidine, astemizole, cisapride and ergotamine. Therapeutic Drug Monitoring, 2004. Christensen, M, et al., The Karolinska cocktail for phenotyping of five human cytochrome P450 enzymes. For example, in China an association was detected between polymorphisms of CYP2E1 and oesophageal and gastric cancer [Inhibition is reduced enzyme activity due to direct interaction with a drug. (see text of other notes for details about each one). 3A4 is the most abundant in the human liver. 5(1): p. 6-13.5. Citalopram / escitalopram are borderline, being significant inhibitors of CYP2D6 even a minimum dose levels. 9(5): p. 442-73.20. Series B: Biological Sciences, 2005. Enzyme inhibition reduces metabolism, whereas induction can increase it. Part of Am J Psychiatry, 1996. This large family of enzymes is classified with numbers and letters, as below, based on their degree of structural homology (similarity). Mutat Res, 2001. 75(5): p. 373-5.17. It is rather like a crowd of people leaving an auditorium.