Pharmacogenomics: Genes and Medicine Response

Read this first

This page explains a research and clinical field. It does not tell anyone which medicine to take, change or stop. The FDA states that patients should not adjust their medications without consulting their prescriber. [1] If you are worried about a medicine, speak to the prescriber or pharmacist who knows your history.

What pharmacogenomics is

Pharmacogenomics (also called pharmacogenetics) uses a person's genomic information to help tailor the selection of drugs used in their medical management. [2] Genes can affect how the body handles a drug (for example how quickly it is broken down) or how a target responds. The idea is that a small number of drugs can be better matched to a person. Genetic information is only one of many factors: the FDA notes a patient's genetic makeup is only one of many factors that may impact drug concentrations and response. [3]

What the US FDA publishes (read 2026-10-22, United States only)

The FDA keeps two public tables.

• Table of Pharmacogenomic Biomarkers in Drug Labeling. It lists drugs whose labeling contains pharmacogenomic information. The labeling for some, but not all, of the products includes specific actions to be taken based on the biomarker information. [4] One example in the table: the labeling for abacavir lists HLA-B in a boxed warning and other sections. [5] That is a statement about one drug's label and does not apply to other medicines.
• Table of Pharmacogenetic Associations. The FDA says it has evaluated these associations and believes there is sufficient scientific evidence that subgroups with certain genetic variants are likely to have altered drug metabolism and, in some cases, different effects. It also says that inclusion of a gene-drug pair does not necessarily mean the FDA advocates using a test before prescribing, and that most listed associations have not been evaluated for the impact of testing on clinical outcomes. [6][7]

Label: approved medicine applies to the specific label statements for named drugs. A table entry is not an endorsement of any particular test.

What human trials show

A 12-gene panel in Europe (PREPARE). In a cluster-randomised crossover implementation study across seven European countries, 6,944 patients receiving a first prescription for a drug covered by guidelines were assigned to genotype-guided treatment or standard care. Clinically relevant adverse drug reactions in 12 weeks occurred in 21.5% of the guided group and 28.6% of controls (odds ratio 0.70, 95% CI 0.61 to 0.79). [8] It was open-label and almost all participants (97.7%) reported European, Mediterranean or Middle Eastern ethnicity, so the findings may not apply equally to everyone. [9] Label: promising but limited, for the specific panel and population studied.

Antidepressant selection in the VA (PRIME Care). In a randomized trial of 1,944 patients with major depression, testing led clinicians to prescribe fewer drugs with predicted drug-gene interactions. Remission was higher over 24 weeks (odds ratio 1.28), but not significantly higher at week 24, and the authors concluded results had small nonpersistent effects on symptom remission. [10] Label: mixed. Fewer predicted interactions is a process measure; remission is the clinical outcome, and it moved only a little.

Both are single trials with their own populations. Neither shows that every genetic test for every drug is useful.

Consumer tests and claims

The FDA says direct-to-consumer tests of this type need FDA premarket review, and that it has not authorized any DTC pharmacogenetic tests that predict whether a person is likely to respond to or have adverse reactions to a specific drug. [11] The FDA has also issued a safety communication about tests making unapproved claims of this kind. [11] Its page lists an authorized over-the-counter pharmacogenetic report about drug metabolism; the listing says that report does not describe whether a person will respond to a particular therapeutic [12] and should not be used to start, stop, or change any course of treatment. [13] The FDA page is marked as current as of 12/20/2019, so check the FDA site for later changes. [14] Treat any website promising to tell you "which medicine works for you" from a saliva kit as a marketing claim. For the broader landscape see Direct-to-Consumer Genetic Tests and Treatment-Response Research and Genetics.

Who this matters for

Anyone who takes several medicines, has had a severe side effect, or is starting a drug with a known gene link may wish to ask a prescriber whether testing is relevant. Pregnancy, children, older adults and people with liver or kidney disease need individual advice. For supplement and herb interactions, which are a separate issue from genes, see How Interactions Work.

Guideline groups

Clinical guideline groups such as the Clinical Pharmacogenetics Implementation Consortium publish drug-gene recommendations for clinicians. Their website could not be read in this session, so no specific recommendations are cited here.