What is pharmacogenomics?
When a medicine is developed for a disease, it should hopefully treat anyone with the disease. But in some cases a medicine might not be effective for someone or even cause serious side-effects. This may be due to their genes. Each of our bodies is unique, including our responses to medications. In this article I talk about pharmacogenomics, the study of how our genes affect how well drugs work.
How does pharmacogenomics work?
Pharmacogenomics combines two fields of study.
- Pharmacology, which is the study of the science of drugs and their actions.
- Genomics, which is the study of genes and how they function.
Our genes are made of DNA, the genetic material in our cells that makes us who we are. We all have DNA and between people our DNA is around 99.9 per cent similar. The difference in our DNA makes us unique. These differences in DNA are called genetic variants
Sometimes we might have a certain disease or increased risk of disease because of our genes. For example, people with a mutation in genes called BRCA1 and BRCA2 have an increased risk of developing breast cancer. Our genes may also affect how well a medicine works for us.
Certain gene variants are known to affect how a drug will work in the body. This link is known as a drug-gene pair. Genetic variants are known for commonly used drugs including:
- antidepressants, for treating mental health conditions
- painkillers, such as codeine
- statins, which are used for treating heart disease
- the contraceptive pill
Genetic variants in your DNA may affect:
- how your body handles a drug (pharmacokinetics)
- what the drug does to your body (pharmacodynamics)
What does pharmacogenomic testing tell you?
Nearly everyone (about 98 per cent) has at least one genetic variant (change) that impacts how a drug works for them. You can only find which ones you might carry through a pharmacogenomics test.
A pharmacogenomics test is done by taking a DNA sample, such as a blood sample. Your DNA is then checked for any possible known gene variants that could affect your response to drugs. So, when a doctor prescribes a medicine to you, by checking your pharmacogenetics profile they can see if it is the right one for you.
If you don’t carry a gene variant for a drug then it is considered safe for you to use that drug. However, if you do have a gene variant, then your doctor will advise if you need to have an alternative. Or you might be still able to use the drug at a lower dose and with close monitoring.
One drug that uses routine pharmacogenomic testing is abacavir, which is used to treat HIV. A variant of genes called HLA genes can cause serious side-effects. So, anyone who is considered for abacavir must be tested for this gene. If they have the gene variant then they cannot be given abacavir.
What are the benefits of pharmacogenomics?
Pharmacogenomics can make medicine more personalised and tailored to your genetic makeup. It can help doctors to prescribe medicines in a way that’s safer and more accurate. This can help make sure you get the right type and dose of medicine when you’re first treated. Pharmacogenomics aims to:
- avoid unnecessary side-effects
- reduce healthcare costs
- reduce hospital admissions
What is precision medicine?
Precision medicine is about making medicine more personalised and tailored to an individual. It may also be called personalised medicine. Genetics is one part of it. But there are other things that can affect how drugs work for you. This includes your age, weight, conditions you have, whether you smoke, and other drugs you’re taking.
Pharmacogenomics in healthcare and personalised medicine is still emerging. Always see a doctor if your medicine isn’t working or if you have serious side-effects. You can also report side-effects to the Medicines and Healthcare Products Regulatory Agency (MHRA) via their Yellow Card scheme.
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Sources Sources
- Personalised prescribing: using pharmacogenomics to improve patient outcomes. Report of a working party. Royal College of Physicians and British Pharmacological Society London. bps.ac.uk, published March 2022
- Rollinson V, Turner R, Pirmohamed M. Pharmacogenomics for Primary Care: An Overview. Genes (Basel). 2020 Nov 12;11(11):1337. doi: 10.3390/genes11111337
- Pattan V, Kashyap R, Bansal V, et al. Genomics in medicine: A new era in medicine. World J Methodol. 2021 Sep 20;11(5):231-242. doi: 10.5662/wjm.v11.i5.231
- Cancer genomics. Genomics England. genomicsengland.co.uk, accessed May 2025
- Personalised medicine. European Commission. ec.europa.eu, accessed May 2025
- Evans W, Meslin EM, Kai J, et al. Precision Medicine-Are We There Yet? A Narrative Review of Precision Medicine's Applicability in Primary Care. J Pers Med. 2024 Apr 15;14(4):418. doi: 10.3390/jpm14040418
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