Clarithromycin: What It Is, How It Works, and What You Need to Know

When you’re dealing with a stubborn infection, your doctor might reach for clarithromycin, a macrolide antibiotic that stops bacteria from growing by blocking protein production. Also known as Biaxin, it’s one of the most prescribed antibiotics for respiratory and skin infections, and even for stomach ulcers caused by H. pylori. Unlike some broad-spectrum drugs, clarithromycin targets specific bacteria without wiping out everything in your gut—though it still can cause digestive upset. It’s not a cure-all, but when used right, it’s a powerful tool.

Clarithromycin is often paired with other drugs, especially for treating H. pylori, a bacteria that causes peptic ulcers and chronic stomach inflammation. You’ll usually see it combined with proton pump inhibitors and amoxicillin in a three-drug regimen. For lung infections like pneumonia or bronchitis, it’s chosen because it penetrates lung tissue well. It’s also used for skin infections like cellulitis, and sometimes for ear infections in kids when other antibiotics fail. But it’s not for every bug—viruses don’t respond to it, and some bacteria have grown resistant over time.

Side effects are common but usually mild: nausea, diarrhea, bad taste in the mouth, or stomach cramps. More serious reactions—like liver problems or irregular heartbeat—are rare but real, especially if you’re taking other meds. That’s why it’s critical to tell your doctor about everything you’re on, including heart medications, blood thinners, or even St. John’s wort. The macrolide class, which includes azithromycin and erythromycin shares similar risks, so if you’ve had a bad reaction to one, you might react to others too.

Clarithromycin isn’t something you take casually. Even if you feel better after a few days, finishing the full course matters—stopping early lets surviving bacteria become stronger. It’s also not safe for everyone: people with liver disease, certain heart rhythm issues, or a history of allergic reactions to similar antibiotics need alternatives. And while it’s sometimes used off-label, like for Lyme disease or certain immune conditions, those uses aren’t backed by strong evidence.

The posts below cover real-world situations where clarithromycin comes up—not just as a standalone drug, but as part of bigger health stories. You’ll find how it fits into treating stomach ulcers, what to do when it doesn’t work, how it interacts with other meds, and why some people end up with side effects that surprise them. Whether you’re taking it now, were prescribed it in the past, or are just trying to understand why your doctor chose it, this collection gives you the facts without the fluff.