Why Winter Is a High-Risk Time for Drug Interactions

January may feel like a fresh start, but it’s also one of the riskiest months of the year for medication mishaps. According to Corey Frederick, Pharm.D., an infectious diseases clinical pharmacist at Baptist Health South Florida, the spike in respiratory infections during winter leads many people to layer new medications, both prescription and over the counter, on top of what they already take. That combination can quietly raise the risk of harmful drug interactions.

When a doctor prescribes a new medication and it’s filled at a pharmacy, pharmacists routinely check it against a patient’s existing prescriptions for safety. But over-the-counter cold and flu products don’t always go through the same safeguards, especially if patients buy them without consulting a pharmacist. Many people assume these products are harmless because they’re easy to access, but that’s not always the case.

Combination cold and flu medications, such as those that treat multiple symptoms at once, are a major source of concern. While convenient, they often contain several active ingredients, like acetaminophen, decongestants and pain relievers, that can interact with prescription medications. For example, someone taking naproxen for chronic pain may unknowingly increase their risk of stomach bleeding if they also take an over-the-counter product containing ibuprofen. Others, including people on certain antidepressants, may experience spikes in blood pressure when using common decongestants.

Supplements and vitamins also play a role. Frederick highlights Saint-John’s-wort as a common example of a “natural” product that can significantly interfere with prescription drugs. It speeds up liver enzymes that metabolize medications, which can cause drugs to leave the body too quickly and become less effective. This can be especially dangerous for people taking medications for heart disease, HIV, organ transplants, mental health conditions or birth control.

Signs of a drug interaction aren’t always dramatic. Symptoms can include stomach upset, dizziness, unusual drowsiness or agitation, and changes in heart rate or blood pressure. Sometimes, the clue is simply that a medication you normally take stops working the way it usually does.

The most effective way to reduce risk is communication. Frederick stresses the importance of keeping an up-to-date medication list, including prescriptions, over-the-counter drugs and supplements, and sharing it with health care providers. He also cautions against relying on internet searches or social media for guidance. Pharmacists and clinicians are trained to evaluate drug interactions using reliable medical evidence, making them the best resource when questions arise.