Azithromycin
Brand names: Zithromax
Azithromycin is a macrolide antibiotic indicated for a range of bacterial infections including respiratory tract, skin and soft-tissue, otitis media and certain sexually transmitted infections, valued for its convenient short courses.
Adult dose
Paediatric dose
Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.
UK SPC, paediatric patients aged 6 months and older weighing <45 kg, single daily dose. Acute bacterial sinusitis / community-acquired pneumonia / acute bacterial skin and skin structure infections: 10 mg/kg/day for 3 days, or 10 mg/kg on day 1 then 5 mg/kg/day on days 2–5. Acute bacterial otitis media: single dose of 30 mg/kg, or 10 mg/kg/day for 3 days, or 10 mg/kg day 1 then 5 mg/kg/day days 2–5. Acute streptococcal tonsillitis and pharyngitis: 20 mg/kg/day for 3 days, or 12 mg/kg/day for 5 days.
Contraindications
- Hypersensitivity to azithromycin, erythromycin, any macrolide or ketolide antibiotic, or any excipient
- History of cholestatic jaundice/hepatic dysfunction associated with prior azithromycin use (US label)
Side effects
- Diarrhoea
- Nausea
- Vomiting
- Abdominal pain
- Headache
Interactions
- QT-prolonging drugs — increased risk of ventricular arrhythmia/torsades de pointes
- Warfarin/oral anticoagulants — may potentiate effect; monitor prothrombin time
- Nelfinavir — increased azithromycin concentrations; monitor for adverse reactions
Clinical monograph
How it works
It inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit and preventing peptide chain elongation, conferring activity against many Gram-positive, atypical and some Gram-negative organisms.
Prescribing in practice
- Because azithromycin can prolong the QT interval, avoid or use with caution in those with known QT prolongation, significant cardiac disease, electrolyte imbalance or other QT-prolonging medicines.
- Rare but serious hepatotoxicity has been reported, and treatment should be stopped if signs of liver injury occur.
- It may interact with drugs such as certain ergot alkaloids and statins, so concomitant therapy should be reviewed.
Monitoring
Routine monitoring is not usually required for short courses, but assess liver function and cardiac risk where clinically indicated.
Counselling the patient
- Finish the full course as prescribed.
- Seek advice if you develop palpitations, fainting or jaundice.
- Let your clinician know about other medicines and any heart conditions.
Evidence & guidelines
Azithromycin is widely used across UK antimicrobial guidance, and the MHRA has issued reminders regarding its potential to prolong the QT interval.
Reference: NICE CKS; BTS pneumonia; BASHH; CF Trust; MHRA Drug Safety Update; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).
Related
Curated clinical cross-links plus same-class fallbacks.
- Centor / McIsaac Score for Strep Pharyngitis · Throat
- FeverPAIN Score for Strep Throat · Throat
- Jarisch-Herxheimer Reaction Severity Assessment · Treatment Reactions
- PID Severity (CDC Diagnostic Criteria) · Gynaecological Infections
- Gustilo-Anderson Classification (Open Fractures) · Fracture Classification
- DRIP Score for Drug-Resistant Pneumonia · Pneumonia
- Infective Endocarditis · ESC 2023 Infective Endocarditis Guidelines; NICE NG41
- Eczema Herpeticum · BAD; NICE CKS
- Suspected Bacterial Meningitis (Adult) · NICE NG240 (2024); NICE NG143 (paeds)
- Clostridioides difficile Colitis · NICE NG199 (2021); IDSA/SHEA 2021
- Returning Traveller — Fever · NaTHNaC; PHE; ESCMID 2018
- Malaria — Diagnosis & Management · PHE 2016; WHO 2023