Azithromycin: Uses, Side Effects, Interactions and Tips

6 min read · Medicines · By the Asthra Health Care team

What azithromycin is used for

Azithromycin is an antibiotic from the macrolide group, which also includes clarithromycin and erythromycin. Doctors prescribe it for some chest infections including atypical pneumonia, bacterial throat and ear infections, sinusitis, some skin infections, certain sexually transmitted infections such as chlamydia, and in some cases for typhoid fever. It is often chosen for people allergic to penicillin.

In India, azithromycin is often misused for colds, viral fevers and coughs. Most of these illnesses are caused by viruses, against which azithromycin has no effect. Misuse has made many bacteria resistant, so it works less well when it is truly needed.

• Some chest infections and atypical pneumonia
• Bacterial throat, ear and sinus infections
• Certain skin and sexually transmitted infections
• Typhoid fever in some situations, as a doctor decides

How azithromycin works

Bacteria need to make proteins to grow and multiply. Azithromycin attaches to the part of the bacterial cell that builds proteins, called the ribosome, and blocks it. This stops the bacteria from growing, giving the body's immune system time to clear the infection.

Azithromycin stays in the body's tissues for a long time, which is why courses are often shorter than for many other antibiotics. The medicine keeps working for some days after the last tablet, so symptoms may continue improving even after the course ends. The exact length of treatment is always decided by the doctor.

Azithromycin side effects: common and serious

Common side effects include loose stools, nausea, stomach pain, vomiting and headache. Taking it as your doctor or pharmacist advises regarding food can reduce stomach upset. Some people notice a change in taste or mild dizziness. These effects are usually mild and pass once the course is finished. Keep sipping fluids if stools are loose.

Serious side effects include changes in heart rhythm, known as QT prolongation, which can rarely cause a dangerous irregular heartbeat, especially in people with heart disease or low potassium or magnesium. Severe allergic reactions and serious skin rashes can occur. Rarely, it causes liver inflammation, hearing changes or severe diarrhoea from Clostridioides difficile infection. It can also worsen muscle weakness in myasthenia gravis.

Who should avoid azithromycin or take extra care

People with a known allergy to azithromycin or other macrolide antibiotics must not take it. Those with heart rhythm problems, a slow heart rate, heart failure, low potassium or magnesium, or a family history of sudden cardiac death need a doctor's assessment first. People with liver disease or myasthenia gravis also need extra care. Elderly people may be more sensitive to heart-rhythm effects.

Azithromycin is used in pregnancy and breastfeeding when a doctor decides it is needed. In children, the amount is based on weight, and it is given only as the doctor prescribes. Tell your doctor about any heart condition in the family, any fainting episodes and all medicines the child or adult already takes, so the safest antibiotic can be chosen for the infection.

Azithromycin interactions to know

Medicines that also affect heart rhythm add to the risk. These include some anti-nausea medicines like domperidone and ondansetron, certain antidepressants and antipsychotics, some heart rhythm medicines like amiodarone, hydroxychloroquine, and fluoroquinolone antibiotics. Water tablets that lower potassium can add to the risk.

Antacids containing aluminium or magnesium can reduce absorption, so a gap between them is usually advised. Azithromycin can increase the effect of warfarin and raise the levels of digoxin and ciclosporin. Always tell your doctor and pharmacist about every medicine you take.

Practical tips for using azithromycin

Azithromycin is only on a doctor's prescription. Never take it on your own for a cold, cough or fever, and never use leftover tablets or share them. Take it exactly as prescribed and do not stop or extend the course without asking your doctor.

Drink enough fluids, rest, and eat light meals if your stomach is upset. Keep a gap between antacids and azithromycin as your pharmacist advises. If a child vomits soon after a dose, ask the doctor or pharmacist what to do rather than repeating it on your own.

When to talk to your doctor about azithromycin

See your doctor if symptoms are not improving after a few days, if fever continues or returns, or if you develop a rash or ongoing diarrhoea. Seek emergency care for palpitations, fainting, swelling of the face or throat, difficulty breathing, blistering skin or yellow eyes. Talk to your doctor or pharmacist whenever you are unsure about an antibiotic.

This article is general health information, not medical advice. Do not start, stop or combine medicines on your own — always follow your doctor's prescription and ask your pharmacist if unsure.