Environmental influences drug-metabolizing enzymes

Ethnic differences have been shown to influence response to psychotropic medications. Much of the focus on the explanation for such differences has been on drug-metabolizing (CYP) enzymes of the liver and their sway over pharmacokinetic factors. It is now well recognized that differences in the distribution of polymorphic variants of CYP enzymes exist between different ethnic groups. However, within ethnic groups there are considerable inter-individual variations in drug kinetics, which may not be accounted for solely by genetic variation. Responses to pharmacotherapy are multifaceted and involve the interaction of environmental and... 

The influence of age on metabolic clearance is less clear than its influence on renal function. Metabolic clearance is more variable between individuals because of the genetic control and the influence of environmental factors on the metabolic capacity. The term metabolism also encompasses many different enzyme reactions that might be influenced to different extents by age, liver disease, or genetic variables. Unlike renal disease, in which creatinine clearance provides a reasonable estimate of kidney function, not one good indicator exists for the degree of liver function impairment with respect to drug metabolizing capacity. 

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