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# Genomic medicine and pharmacogenomics

Using a person's genome to choose drugs and doses, screen populations and diagnose sick newborns quickly.

Updated Nov 13, 2026

## Key facts

- Pharmacogenomics studies how inherited variants change drug response; expert groups (such as CPIC) publish gene–drug guidelines.
- HLA-B*57:01 predicts hypersensitivity to abacavir, so it is tested before treatment; HLA-B*15:02, frequent in South-East Asian ancestry, predicts severe skin reactions to carbamazepine.
- CYP2C19 poor metabolisers activate clopidogrel poorly; CYP2D6 ultrarapid metabolisers turn codeine into too much morphine, which has caused deaths in children.
- TPMT and NUDT15 variants make thiopurines (azathioprine, mercaptopurine) toxic to the marrow; DPYD variants make fluorouracil and capecitabine toxic; CYP2C9 and VKORC1 affect warfarin needs.
- Population genetic screening: newborn screening for treatable disorders and cascade testing of relatives once a family variant is known.

## In detail

- Drug response is usually a complex trait: several genes plus age, organ function, interactions and adherence all play a part.
- Rapid genome sequencing in critically ill newborns can give a diagnosis within days and change treatment.
- Tumour sequencing chooses targeted cancer drugs; germline findings in the tumour report may reveal hereditary cancer.
- G6PD deficiency is a gene–drug interaction too: oxidant drugs such as primaquine and rasburicase cause haemolysis.
- Polygenic risk scores may later refine screening, but are not yet standard care.

**Also called**
Precision medicine, Gene–drug pairs

## Clinical notes

- Ask about previous drug reactions in relatives; a family history of anaesthetic death suggests malignant hyperthermia susceptibility (RYR1).
- Pharmacogenetic results last a lifetime and should be recorded where every prescriber can see them.

## Test yourself

Think of the answer, then tap the question to see it.

## Which test is done before starting abacavir?

HLA-B*57:01; carriers have a high risk of hypersensitivity and should not receive the drug.

## Why is codeine dangerous in CYP2D6 ultrarapid metabolisers?

They convert codeine to morphine quickly, which can cause life-threatening opioid toxicity.

## Which gene variants predict severe thiopurine toxicity?

TPMT and NUDT15.

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## Connections

## Related conditions 4

- [Glucose-6-phosphate dehydrogenase (G6PD) deficiency](https://durgical.com/en/conditions/glucose-6-phosphate-dehydrogenase-deficiency/)
- [Malignant hyperthermia](https://durgical.com/en/conditions/malignant-hyperthermia/)
- [Familial hypercholesterolemia](https://durgical.com/en/conditions/familial-hypercholesterolemia/)
- [Lynch syndrome (hereditary non-polyposis colorectal cancer)](https://durgical.com/en/conditions/lynch-syndrome/)

## Related 6

- [Cytochrome P450 system](https://durgical.com/en/biochemistry/topics/cytochrome-p450-system/)
- [Xenobiotic biotransformation: phases I, II and III](https://durgical.com/en/biochemistry/topics/xenobiotic-biotransformation-phases-i-ii-and-iii/)
- [Genetic tests: what each one finds](https://durgical.com/en/biochemistry/topics/genetic-tests-what-each-one-finds/)
- [Newborn screening](https://durgical.com/en/biochemistry/topics/newborn-screening/)
- [Complex traits: familial risk, twins, heritability and polygenic scores](https://durgical.com/en/biochemistry/topics/complex-traits-familial-risk-twins-heritability-and-polygenic-scores/)
- [Pyrimidine degradation and β-alanine](https://durgical.com/en/biochemistry/topics/pyrimidine-degradation-and-alanine/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [What is pharmacogenomics?: MedlinePlus Genetics](https://medlineplus.gov/genetics/understanding/genomicresearch/pharmacogenomics/) (MedlinePlus, US National Library of Medicine, 2026); [Pharmacogenomics](https://www.genome.gov/genetics-glossary/Pharmacogenomics) (National Human Genome Research Institute (NHGRI), 2026); [What is precision medicine?: MedlinePlus Genetics](https://medlineplus.gov/genetics/understanding/precisionmedicine/definition/) (MedlinePlus, US National Library of Medicine, 2026); [ClinPGx (CPIC guidelines)](https://cpicpgx.org/) (Clinical Pharmacogenetics Implementation Consortium (CPIC) and PharmGKB, 2026).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/topics/genomic-medicine-and-pharmacogenomics/