Azithromycin (Zithromax): uses, side effects and cautions

The NHS names chest infections including pneumonia, ear, nose and throat infections such as sinusitis, skin infections, Lyme disease and some sexually transmitted infections. People prone to repeated chest infections may also be given it as a long-term preventive.

It is a macrolide, like clarithromycin and erythromycin. The NHS says macrolides work by killing the bacteria that cause the infection, and that azithromycin is taken once a day whereas clarithromycin is twice daily and erythromycin up to four times.

Take azithromycin at about the same time each day. The adult amount quoted by the NHS is 500 mg a day for 3 to 10 days depending on the infection, although some conditions are treated with a one-off 1 g or 2 g dose. Your own instructions are what count.

Capsules and tablets should be taken at least an hour before food or two hours after it. The liquid does not have this restriction. Measure liquid with the syringe or spoon supplied.

• Finish the course even if you feel better, to stop the infection returning.

• Missed dose: take it when you remember unless the next is near; do not double up.

• Taking one extra dose is unlikely to cause serious harm but may trigger temporary side effects; call NHS 111 if you took more than one extra.

Most adults and children can take azithromycin. The NHS lists allergy to azithromycin or other medicines, liver or kidney problems, heart conditions including arrhythmia, previous diarrhoea caused by antibiotics and myasthenia gravis as points to raise.

The liquid contains sugar, so people with diabetes should mention it.

Common effects, in more than 1 in 100 people, include nausea, diarrhoea, vomiting, loss of appetite, headaches, dizziness or tiredness and altered taste. The NHS suggests simple meals, fluids and getting up slowly from sitting; avoid driving or machinery if dizzy.

• Call NHS 111 or a doctor for an irregular or rapid heartbeat, yellowing skin or eyes, pale stools with dark urine, ringing in the ears, hearing loss or unsteadiness, severe stomach or back pain, blood in the urine or persistent diarrhoea with blood or mucus.

• Call 999 for chest pain or for anaphylaxis: swollen lips, mouth or throat, breathing difficulty, confusion or collapse.

The NHS names warfarin, dabigatran and edoxaban; heart rhythm medicines such as amiodarone and sotalol; ciclosporin and tacrolimus; simvastatin and atorvastatin; ergotamine and dihydroergotamine; colchicine; digoxin; rifabutin; and antacids. It says the list is extensive, so check with a pharmacist.

Not enough is known about herbal remedies alongside azithromycin to call them safe.

The NHS says azithromycin can be used in pregnancy if needed, though other antibiotics may be more suitable depending on the infection. It is generally acceptable while nursing a healthy baby, with watching for feeding difficulties, rash, thrush, diarrhoea or drowsiness. There is no good evidence it affects fertility.

Alcohol is fine unless you feel dizzy, and you should only drive if the medicine does not make you dizzy. It does not stop contraception working, but vomiting or prolonged diarrhoea can reduce the pill. Report suspected side effects through Yellow Card.