**Part 3**

**Pharmacogenetic** 

176 Pharmacology

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by in vitro and in vivo activated hepatic stellate c

**9** 

Bosun Banjoko

*Nigeria* 

*Obafemi Awolowo University, Ile-Ife,* 

**Pharmacogenetics: The Scientific Basis** 

The history of genetic variations in drug responses can be traced to the 1950s with the observations that muscle relaxant suxamethonium chloride and drugs metabolized by Nacetyl transferase exhibit differences in response in patients. One in 3500 caucasians was found to possess the less efficient variant of the enzyme, butyryl chlolinesterase that metabolizes suxamethonium chloride; an anaesthetic agent.As a consequence, the drug's

The term pharmacogenetics evolved from the combination of two areas of study namely pharmacology and genetics. Pharmacology is the study of how drugs work in the body and genetics is the study of how characteristics that result from the action of genes acting together are inherited and how they function in the cells of the body . Therefore, pharmacogenetics refers to genetic differences in metabolic pathways which can affect individual responses to drugs both in terms of therapy and adverse effects. Pharmacogenetics helps our understanding of why some individuals respond to drugs and others do not and why some

In addition, pharmacogenetic information helps the physician to identify those patients who

A recent offshoot of pharmacogenetics, termed pharmacogenomics is the study of drug response in the context of the entire genome. Pharmacogenomics facilitates information on variations in all the genes in a group of individuals simultaneously to determine the basis of variants in drug response. It is therefore not uncommon to find the two being used interchangeably.However for the purpose of this chapter, pharmacogenetics will be the focus. Individual variation in response to drug ranges from failure to respond to drug therapy to drug to drug interactions when several drugs are taken simultaneously. The clinical consequences range from patients' discomfort through serious clinical illness to the occasional fatality. Approximately 7% of patients are affected by adverse drug reactions, increasing the overall hospital costs by 19% and drug costs by 15%. Some 0.3% of adverse

Variation in drug metabolism and drug response among individuals of the same body weight and on the same drug dose can be due to temporary causes such as transient enzyme

effect is prolonged with slower recovery from surgical paralysis.

require higher or lower doses to achieve optimal therapeutic responses.

will respond favourably to therapy or develop side effects.

drug reactions have fatal outcome (Topic 2010).

**1.1 Individual variation in drug effects** 

**1. Introduction** 
