For millions of Americans, taking medication is a routine and necessary part of maintaining health, but if you’ve watched drug advertisements on TV, you’re familiar with the litany of possible side effects. Many of us have experienced some – perhaps drowsiness from an antihistamine, nausea after one of the new GLP-1 weight-loss shots, or an episode of low blood pressure from a hypertension drug. For some people, a prescribed drug can trigger a severe, even life-threatening, reaction.
These adverse drug reactions (ADRs) are not only dangerous to patients but also place a massive financial burden on healthcare systems: They lead to increased healthcare costs through hospital admissions, longer hospital stays, emergency room visits, and the need for additional treatments to manage the reactions. In the U.S., the costs may be as much as $30.1 billion annually.
However, a groundbreaking new study from British researchers suggests that genetic testing for just three specific genes before a prescription is even written could avoid up to 75% of ADRs. Published in PLOS Medicine, this research highlights how pharmacogenomic (PGx) testing could revolutionize medicine and reduce costs by making drug prescribing safer.
The Genetic Clues Behind Adverse Drug Reactions
Not everyone processes medication in the same way. Our bodies metabolize drugs using enzymes, which are controlled by our genes. Variations in these genes – and, therefore, in the enzymes they express -- can make a person metabolize a drug too quickly or too slowly, leading to dangerous side effects.
The study analyzed over 1.3 million ADR reports collected by the Yellow Card scheme, the U.K.’s official system for tracking medication side effects, and the findings were striking:
Nine percent of ADRs were linked to drugs that interact with three key genes — CYP2C19, CYP2D6, and SLCO1B1 – that play a crucial role in how the body processes many commonly prescribed medications. Those ADRs were, therefore, considered to be “mitigatable,” or avoidable, by pre-administration genetic testing.
The study found that certain classes of drugs were disproportionately linked to ADRs that could be prevented with genetic testing:
- Psychiatric Medications: Accounting for 47% of all genetically linked ADRs, these include antidepressants and antipsychotics, which can cause severe side effects in people with specific genetic variants.
- Cardiovascular Medications: Responsible for 24% of preventable ADRs, these drugs are commonly used for heart conditions and blood pressure management.
A Simple Test with Major Benefits
Genetic testing for CYP2C19, CYP2D6, and SLCO1B1 could allow doctors to personalize prescriptions and adjust drug choices and dosages based on a patient’s genetic makeup. This approach is neither theoretical nor completely new — previous research, including the international PREPARE trial, whose results were reported in 2023, had already shown that some PGx testing can reduce ADRs by approximately 30% when incorporated into routine prescribing.
Who Would Benefit the Most?
The study also highlighted disparities in drug metabolism across different populations. Certain genetic variations are more common in specific ethnic groups: People of African and Asian ancestry appear to be at higher risk for some ADRs. Unfortunately, ethnic data were not available in the Yellow Card reports, but based on known genetic differences, PGx testing could disproportionately benefit these underrepresented groups and help reduce health inequalities.
Why Hasn’t Pharmacogenomic Testing Become Standard Practice?
Despite its clear benefits, PGx testing is not yet widely used in healthcare systems like the U.K.’s National Health Service or in large Health Maintenance Organizations (HMOs) in the U.S. and elsewhere. Some of the barriers include:
- Cost and infrastructure: Implementing routine genetic testing requires investment in laboratory capabilities and integration of data into electronic health records.
- Awareness and education: Many healthcare providers are not yet trained to interpret PGx test results or apply them to clinical decision-making.
- Regulatory and ethical concerns: There are ongoing discussions about how genetic data should be stored and used while protecting patient privacy.
The Takeaway: Safer, Personalized Medicine is Within Reach
The idea of tailoring medicine to an individual’s genetic profile is no longer science fiction — it has become an achievable reality. Pharmacogenomic testing offers a clear path to safer, more effective treatment, particularly for patients on psychiatric and cardiovascular medications.
As healthcare systems evolve, integrating genetic testing into routine prescribing could become one of the most important innovations in modern medicine — saving lives, reducing costs, and making treatment more personalized. We need a crash program to implement it.
Henry I. Miller, MS, MD
Henry I. Miller, MS, MD, is the Glenn Swogger Distinguished Fellow at the American Council on Science and Health. His research focuses on public policy toward science, technology, and medicine, encompassing a number of areas, including pharmaceutical development, genetic engineering, models for regulatory reform, precision medicine, and the emergence of new viral diseases. Dr. Miller served for fifteen years at the US Food and Drug Administration (FDA) in a number of posts, including as the founding director of the Office of Biotechnology.
