Individuals can react differently to the same medicines because of differences in their diet, environment, age, health and genetics. Pharmacogenetics looks at how tiny genetic changes between individuals can greatly affect how they respond to drugs.
Genes change how you react to a drug
Everyone has very slightly different genes in their DNA, which is what makes us individual. These differences can also be in the genes that tell our body how to make the proteins involved in processing drugs, such as drug transporters and enzymes that break them down (metabolise them). These in turn lead to differences in how we respond to the drug.
For example, a gene that carries the instruction to make a drug metabolising enzyme may come in 'fast' and 'slow' allelic forms. Someone whose body makes the 'slow' form may take longer to remove a drug from their bloodstream than someone else with the 'fast' allele. This means that the person with the 'slow' enzyme allele will require less of the drug as it is not metabolised as fast.
In the case of warfarin (a blood thinning drug), a patient with the 'slow' allele for this drug will have an increased risk of bleeding (haemorrhage) if given the same dose as a patient with the 'fast' allele.
Pharmacogenetics is a broad term which covers the following topics:
- how single or multiple genes (up to the whole genome) affect your reaction to a drug.
- how genetic variations affect how your body processes a drug (such as whether you are a fast or slow metaboliser of it).
- what the drug does to a body.
Why Study Pharmacogenetics?