Clarithromycin — quick, practical facts for patients

If your doctor prescribed clarithromycin, you probably want clear, usable info — not a textbook. Clarithromycin (brand name Biaxin) is a macrolide antibiotic doctors use for common infections like bronchitis, pneumonia, sinusitis, and some skin infections. It works by stopping bacteria from multiplying so your immune system can finish the job.

Keep the full course. Even if you feel better in a day or two, stopping early raises the chance the bacteria survive and become resistant. If you miss a dose, take it as soon as you remember unless it's almost time for the next one — then skip the missed dose. Don’t double up.

How clarithromycin is used

Typical adult dosing varies by infection. For bronchitis or sinusitis doctors often prescribe 250–500 mg twice daily for 7–14 days. For pneumonia the dose and length can be higher or combined with other drugs. Kids get weight-based doses. Your prescriber will pick the right dose and duration — don’t change it on your own. Clarithromycin comes as tablets, extended-release tablets, and liquid.

Take it with or without food depending on the formulation. Swallow tablets whole. If you’re using the liquid, shake well and measure carefully with a proper spoon or syringe. Store the medicine as the label says and finish the bottle unless directed otherwise.

Side effects and interactions

Common side effects are stomach upset, diarrhea, taste changes, and mild headache. Most go away after treatment ends. More serious problems are rare but include liver issues, allergic reactions, and heart rhythm changes (QT prolongation). If you get severe stomach pain, jaundice, fast/irregular heartbeat, or a serious rash, get medical help right away.

Clarithromycin interacts with several drugs. It can raise levels of statins, some blood thinners like warfarin, certain antiarrhythmics, and drugs that affect the heart rhythm. Avoid combining clarithromycin with strong CYP3A4 substrates unless your doctor adjusts doses. If you’re on other medicines, tell your prescriber and pharmacist before starting clarithromycin.

Pregnancy and breastfeeding: ask your provider. Clarithromycin is usually avoided in pregnancy unless there’s no safer option. If you breastfeed, discuss whether to pause or switch medications and watch the baby for unusual symptoms.

Thinking of buying antibiotics online? Use reputable pharmacies and require a prescription. Our site has guides on safe online pharmacies, comparing providers and spotting risky vendors. If cost or access is an issue, talk to your clinician about alternatives or patient assistance programs.

Questions you can bring to your clinician: Do I need this antibiotic for my condition? What dose and how long? Any interactions with my current meds? What side effects should I watch for? Clear answers will keep treatment safe and effective.

Need more reading? Check our related guides on antibiotic choices, drug interactions, and safe online pharmacies for practical tips while you’re on treatment.