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Safety information · Internal patient-safety page

Azithromycin safety summary

Azithromycin is a macrolide antibiotic used to treat chlamydia and other bacterial infections. It concentrates inside tissue and keeps working for several days after the last tablet, which is why a chlamydia course can be as short as a single dose.

Azithromycin

What it's used for

  • Take exactly as prescribed: for chlamydia this is often a single dose taken at once.
  • Can be taken with or without food; food can ease a sensitive stomach.
  • Avoid sex (including with condoms) for 7 days after a single-dose treatment, and until any partner has also been treated.
  • Complete the full prescription even if symptoms settle early.

Most common side effects

  • Diarrhoea or loose stools.
  • Nausea, abdominal pain, wind.
  • Headache.
  • Dizziness.
  • Changes in taste.

Serious side effects: stop and seek care

  • Severe allergic reaction: rash, swelling of the face or throat, difficulty breathing.
  • Severe skin reactions with blistering or peeling.
  • Palpitations, a racing or irregular heartbeat, or fainting: azithromycin can prolong the heart's QT interval, especially alongside other medicines that do the same.
  • Yellowing of the skin or eyes, dark urine (liver problems).
  • Severe, watery or bloody diarrhoea, even weeks after finishing, can signal a C. difficile gut infection.

Who should not take it

  • Allergy to azithromycin, erythromycin or any other macrolide antibiotic.
  • A previous episode of jaundice or liver problems caused by a macrolide.
  • Severe liver disease: discuss with the doctor first.
  • Use extra caution with a known long-QT condition, a very slow heartbeat, or low blood potassium or magnesium.

Interactions to flag

  • Other medicines that prolong the QT interval: some antiarrhythmics, antipsychotics and antidepressants.
  • Antacids containing aluminium or magnesium: take azithromycin at least 1 hour before or 2 hours after.
  • Ergot derivatives (for migraine): do not combine.
  • Ciclosporin, digoxin and colchicine: levels can rise; monitoring may be needed.
  • Warfarin and similar anticoagulants: bleeding tendency can increase.

Message us in the app chat if you notice any of these

  • Rash, facial swelling or trouble breathing: call emergency services first.
  • Palpitations, an irregular heartbeat or a fainting episode.
  • Severe or bloody diarrhoea, during treatment or in the weeks after.
  • Symptoms that have not improved a week after treatment.
AEMPS CIMA: Azithromycin 500 mg

This page summarises information from the regulator-approved leaflet for reference only. It does not replace the full leaflet, linked on this page, it is not medical advice and it does not replace the assessment of an EU-licensed doctor. Your doctor will review your individual history, dose and interactions during your consultation.

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