Individual variation in drug

CYP2C19 is another example of the existence of both cross-ethnic and inter-individual variations in drug metabolism. This enzyme is involved in the metabolism of many psychotropics such as diazepam and tertiary tricyclic antidepressants, as well as one of the selective serotonin re-uptake inhibitors (SSRIs), citalopram. Using S-mephenytoin as the probe, previous studies showed that up to 20% of East Asians (Chinese, Japanese, and Koreans) are PMs, when only 3-5%... 

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... 

Although there are individual variations in drug reaction and in the nature of the therapy sessions, the first two or... 

This classification fails to recognise individual variation in drug use. Alcohol can be used in heavy doses that are gravely disabling and induce severe physical dependence with convulsions on sudden withdrawal i.e. for the individual the drug is hard. But there are many people mildly psychologically dependent on it who retain their position in home and society. 

TABLE 13.1-2. Selected Drug Transporters Associated with Individual Variations in Drug Response... 

Narrow therapeutic index combined with the inter-individual variations in drug pharmacokinetics, response, and toxicity adds uncertainty to the clinical trials and use of novel anticancer agents. Pharmacogenetic and metabolomic profiling of the patients promise to at least partly address these concerns, thus helping in the individualization of medication for patients and improved... 

The impact of variations in the bioavailability on the efficacy and safety of an active substance can be easily understood from these figures. The effect of individual variations in drug sensitivity in relation to variations in drug absorption can also be demonstrated. Examples are given in the box. 

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