Pharmacogenomics: How Your Genes Affect Medication Response
When you take a pill, your body doesn’t just absorb it — it pharmacogenomics, the study of how your genes affect how you respond to drugs. Also known as personalized medicine, it’s why one person can take a standard dose of warfarin and stay stable, while another needs half that amount to avoid bleeding. This isn’t guesswork — it’s biology written in your DNA.
That same biology affects how your liver breaks down drugs like CYP2D6, a key enzyme that processes over 25% of common medications, including antidepressants and painkillers. If you’re a slow metabolizer, you might build up toxic levels of tamoxifen or antidepressants. If you’re ultra-rapid, the drug might not work at all. That’s why some people get brain fog from medications others tolerate fine — it’s not the drug, it’s your genes. And it’s not just about side effects. Pharmacogenomics explains why some patients with breast cancer don’t respond to tamoxifen, why certain antibiotics trigger dangerous heart rhythms in some, and why your INR levels swing wildly on warfarin despite sticking to the same diet.
Doctors don’t test everyone yet — but they should. Genetic testing for drug metabolism, how your body processes and eliminates medications is already used in cancer care, mental health, and heart disease. It’s not science fiction. It’s in the research behind why some antidepressants fail in teens, why clopidogrel doesn’t work for some heart patients, and why pill splitting can be risky if your body handles the dose differently. This isn’t about fancy labs or expensive tests for everyone. It’s about understanding why your medication works — or doesn’t — and what to ask your doctor next.
Below, you’ll find real cases where genetics changed outcomes: how a simple gene variant made azithromycin dangerous for one patient but safe for another, why some people can’t use SSRIs with tamoxifen, and how a single drug interaction with cimetidine can send someone to the ER. These aren’t rare exceptions. They’re patterns hidden in plain sight — and now you know where to look.
