Roxithromycin

Key facts

• Roxithromycin (sold as Rulide, among other brands) is a macrolide antibiotic. It stops susceptible bacteria from making the proteins they need to grow and multiply.
• You usually take it twice a day, on an empty stomach, for a course lasting 5 to 10 days depending on the infection.
• Roxithromycin can prolong the heart's QT interval. Do not combine it with other medicines that also affect heart rhythm, and tell your doctor if you have a known heart-rhythm disorder.
• Seek urgent care for severe, watery diarrhea, yellowing of the skin or eyes, or signs of an allergic reaction.

What roxithromycin treats

Roxithromycin treats bacterial infections of the respiratory tract, including bronchitis, sinusitis and tonsillitis, as well as skin and soft-tissue infections. It only works against bacteria, not viruses, so it will not help a cold or flu. Always finish the full course your doctor prescribes, even if you feel better early, to stop the infection returning and reduce the chance of resistant bacteria developing.

How roxithromycin works

Bacteria need to manufacture proteins to grow and divide. Roxithromycin attaches to part of the bacterial ribosome, the cell structure that builds these proteins, and blocks the process. This stops the bacteria multiplying, letting your immune system clear the remaining infection.

Before you take it

• Do not take roxithromycin if you have had an allergic reaction to it or to other macrolide antibiotics, such as erythromycin or clarithromycin.
• Tell your prescriber if you have liver disease, a heart-rhythm disorder, or if you take other medicines known to affect the QT interval, including some antiarrhythmics, antipsychotics and other antibiotics.
• Roxithromycin can raise blood levels of some other medicines, including certain drugs that affect blood clotting and heart rhythm. Tell your prescriber about everything else you take.
• Use during pregnancy or breastfeeding only if your doctor considers it necessary.

Side effects

Common effects include nausea, stomach cramps, diarrhea, a metallic taste, and headache.

Stop and seek urgent medical care for any of these:

• Severe, watery or bloody diarrhea, which can signal a serious intestinal infection.
• Yellowing of the skin or eyes, dark urine, or persistent abdominal pain, which can signal liver injury.
• Hives, facial or throat swelling, or difficulty breathing.
• A fast, irregular heartbeat or fainting.

Safety essentials

• Roxithromycin can prolong the QT interval and trigger a dangerous heart rhythm. Never combine it with other QT-prolonging drugs without medical advice, and get urgent care for a fast or irregular heartbeat.
• Complete the full prescribed course. Stopping early lets surviving bacteria regrow and encourages resistance.
• If diarrhea becomes severe or persists after the course ends, contact your doctor. This can indicate a Clostridioides difficile infection that needs specific treatment.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.