Drug Interactions with Terbinafine: What You Need to Know

When you take terbinafine, an antifungal medication used to treat nail and skin infections. It's known for being effective, but it doesn't play well with everything else in your medicine cabinet. Many people don’t realize that even a common painkiller or heart pill can turn a simple treatment into a risky situation. Terbinafine is processed by your liver, and it can mess with how other drugs get broken down—especially ones that rely on the same enzyme system, CYP2D6. That’s why mixing it with certain antidepressants, beta-blockers, or antiarrhythmics can lead to unexpected side effects or even dangerous buildup in your blood.

One of the biggest red flags is combining terbinafine with CYP2D6 substrates, drugs that depend on this liver enzyme to be metabolized. fluoxetine, paroxetine, and metoprolol are common examples. If you’re on any of these, your doctor needs to know you’re taking terbinafine—because the interaction can raise the risk of dizziness, slow heart rate, or even serotonin syndrome. And it’s not just prescriptions. Some OTC cold meds and herbal supplements like St. John’s wort can also interfere. Even if you feel fine, your liver might be working overtime, and that’s something you can’t see or feel until it’s too late.

Another layer? Terbinafine can affect liver enzymes themselves. That’s why your doctor might check your liver function before and during treatment, especially if you’re older, have existing liver issues, or take multiple meds. You’ll find posts here that dig into how drug interactions show up in real life—like how polypharmacy increases risks, how blood thinners and NSAIDs create hidden dangers, and why knowing your full med list matters more than you think. These aren’t theoretical concerns. People end up in the ER because they didn’t connect the dots between their antifungal and their daily pills.

What you’ll find below isn’t just a list of articles. It’s a practical toolkit. You’ll see real examples of how medications interact—like how gemfibrozil and fenofibrate can clash, how carbamazepine affects other drugs, and how even something as simple as a diabetes pill can change how your body handles antivirals or antifungals. If you’re on terbinafine, or thinking about it, these posts help you ask the right questions before you take that next pill.