Abstract
As many of us can attest from personal experience, not everyone has the same response to any given medication. Some of us might find that a specific medication improves our symptoms, whereas others find that it does not. Some of us find that a given medication improves our symptoms, but we choose not to use it because it has untoward effects. The bases for such varied response to pharmacotherapies are many. Age, organ function, concomitant medications, gender, diet, and other factors all influence how individuals respond to drugs. However, genetic variation, an additional contributor to drug response, is increasingly recognized as a critical determinant of the effectiveness and safety/tolerability of pharmacological agents.
The human genome is composed of an estimated 3 billion basepairs. Of these, roughly 0.01%, or 3 million, are variable. Variability of genetic sequence takes a variety of forms, including insertions and deletions of nucleotides, but is most commonly found as single-nucleotide polymorphisms (SNPs). SNPs are distinguished from mutations based on their frequency of occurrence in the population; if the variation occurs in more than 1% of the population, it is described as a SNP, whereas a variation occurring in less 1% of the population is referred to as mutation. Many SNPs have no impact on gene function. However, some occur in coding regions and result in truncation or altered formation of the resultant gene product. SNPs occurring outside of coding regions, particularly in promoters and splice sites, can also have profound impacts on the amount or function of the resultant gene product. The study of the effects of genetic variation on drug response is known as pharmacogenetics (1–5).
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McCullough, K. (2006). Personalized Medicine. In: Coleman, W.B., Tsongalis, G.J. (eds) Molecular Diagnostics. Humana Press. https://doi.org/10.1385/1-59259-928-1:341
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