Contraindications: What Medications You Should Never Take Together

When we talk about contraindications, conditions or factors that make a particular treatment inadvisable or unsafe. Also known as drug warnings, these are the red flags your doctor or pharmacist checks before handing you a prescription. They’re not just fine print—they’re the difference between healing and hospitalization.

Take NSAIDs, nonsteroidal anti-inflammatory drugs like ibuprofen or naproxen used for pain and inflammation. For someone with kidney disease or on blood thinners, NSAIDs can trigger dangerous bleeding or sudden kidney failure. That’s a classic contraindication. Same goes for St. John’s Wort, a popular herbal supplement often used for mild depression. It doesn’t just cause side effects—it can strip the power right out of birth control pills, antidepressants, or even heart meds. One study found it cuts blood levels of some drugs by over 50%. That’s not a mild interaction. That’s a medical emergency waiting to happen.

And it’s not just herbs or over-the-counter stuff. Even common prescriptions clash in ways people don’t expect. Terbinafine, an antifungal pill used for nail infections, can interfere with beta-blockers and antidepressants, raising the risk of heart rhythm problems. 5-HTP, a supplement some take to boost mood or sleep, can trigger serotonin syndrome when mixed with SSRIs—symptoms include high fever, confusion, seizures, and even death. These aren’t rare cases. They show up in ERs every week.

Contraindications aren’t just about pills. They’re about your whole health picture: your age, your liver function, your other conditions, even what you eat. Someone with Wilson’s disease can’t take copper supplements. Someone with asthma might react badly to aspirin. A diabetic on allopurinol needs careful monitoring because the drug changes how their body handles uric acid. Every condition you have adds another layer to the puzzle.

That’s why you can’t just rely on the bottle label. Pharmacists write notes for a reason. Your doctor’s instructions aren’t just suggestions—they’re lifesaving details. And if you’re taking five or more meds, you’re already in the high-risk zone for polypharmacy errors. The more pills you take, the more chances for hidden clashes. That’s why checking for contraindications isn’t a one-time thing. It’s an ongoing conversation with your care team.

Below, you’ll find real-world examples of these dangers—how antibiotics trigger C. diff, why mixing blood thinners with NSAIDs is a bad idea, and how even something as simple as peppermint oil can interact with your prescriptions. These aren’t theory. These are cases real people faced. You’ll learn how to spot the warning signs, what questions to ask, and how to protect yourself before the next prescription hits your counter.