Every one of nearly 100,000 Americans in a federal study carried a gene variant that changes how some medicines work

Everyone in a study of nearly 100,000 Americans carried at least one gene variant that can change how well some medicines work or how likely they are to cause side effects, according to a University of Pittsburgh-led study published Nov. 11 in Science Translational Medicine.  And 24.4% had already been prescribed a drug that doctors’ guidelines say should be dosed or chosen differently for someone with their genes.

The findings suggest genetic testing before prescribing, called pharmacogenomic testing, could help many patients, the researchers said.  Almost everyone in the study, 99.5%, had a genetic result that comes with a published prescribing recommendation for at least one drug.

What readers can do

• If you have already had a pharmacogenomic test, share the results with your pharmacist and every doctor who prescribes for you, so they go into your medical record, said senior author Philip Empey, a University of Pittsburgh pharmacy professor.
• Testing is already used before some treatments, Empey said, such as clopidogrel, a blood thinner given after a heart stent, and a chemotherapy drug for colon cancer that can cause serious harm in up to 8% of patients with certain variants.  People taking many medicines at once may also benefit.
• Ask your doctor or pharmacist whether testing makes sense for you.  More than 300 medicines carry gene information on their labels, Empey said.  Don’t stop or change a prescribed medicine on your own.

What the study found

• Participants carried a median of nine variants across the 16 genes studied, according to the university.
• The affected drugs people had most often taken were ondansetron for nausea, ibuprofen for pain, omeprazole and pantoprazole for heartburn and acid reflux, and atorvastatin for cholesterol.
• The team found more than 17,000 variants not reported before, and many variant frequencies differed from earlier estimates, especially in people with roots in the Americas and Africa.

How the study was done

The researchers used whole-genome sequences and electronic health records from participants in All of Us, a National Institutes of Health program that aims to enroll 1 million people across the U.S.  They looked at 16 genes known to affect how drugs are absorbed, broken down or tolerated.  Having a variant does not mean a drug will fail or cause harm, and the study did not track whether patients actually had problems.  Whether to test everyone is still being weighed against the cost, Empey said.

Source:  Haddad et al., “Frequency of pharmacogenomic variation and medication exposures among participants in the All of Us Research Program,” Science Translational Medicine, Nov. 11, 2026.