Macrolide Antibiotic (Azalide)
Pregnancy: There is a large amount of observational data (more than 7000 exposed pregnancies); most studies do not suggest an increased risk of adverse foetal effects such as major congenital or cardiovascular malformations, and epidemiological evidence on miscarriage after early-pregnancy exposure is inconclusive. Azithromycin should only be used during pregnancy if clinically needed. It is excreted in human milk to a substantial extent — decide whether to discontinue breast-feeding or to discontinue/abstain from therapy, weighing the benefit of breast-feeding for the child against the benefit of therapy for the woman.
Azithromycin
Brand names: Zithromax
Azithromycin is a macrolide antibiotic used for a range of respiratory, skin and soft tissue, and sexually transmitted infections, valued for its long half-life and short treatment courses.
Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.
Adult dose
Dose:500 mg once daily for 3 days, or 500 mg on day 1 followed by 250 mg once daily on days 2-5 (acute streptococcal tonsillitis and pharyngitis; acute bacterial sinusitis; acute bacterial otitis media; acute exacerbations of chronic bronchitis, adults only; community-acquired pneumonia; acute bacterial skin and skin structure infections). Urethritis and cervicitis caused by Chlamydia trachomatis: 1000 mg as a single dose
Route: Oral — powder for oral suspension after reconstitution, taken as a single daily dose with or without a meal; administration immediately before a meal may enhance gastrointestinal tolerability. Shake the bottle before each new dose
Frequency: Once daily (single dose for chlamydial urethritis and cervicitis)
PROVENANCE: the bundled eMC source is the SPC for Azithromycin 200mg/5ml Powder for Oral Suspension, and its adult table is headed 'Adults and adolescents weighing at least 45 kg and unable to swallow solid pharmaceutical forms' — for patients who can swallow solids, confirm against the corresponding tablet/capsule SPC. This bundle contains no intravenous posology; for IV therapy refer to the SPC of the azithromycin IV formulations. No absolute adult maximum dose is stated: the paediatric tables reference the adult ceiling with the footnote '# not to exceed the adult daily dose of 500 mg', but the licensed single 1000 mg dose for chlamydial urethritis and cervicitis exceeds that figure, so no maxDose has been recorded. Community-acquired pneumonia: in adults, oral treatment may also follow intravenous treatment if clinically indicated, to complete a 7- to 10-day total course. Acute exacerbations of chronic bronchitis is an adults-only indication. Consideration should be given to the treatment regimens, doses and duration of treatment recommended in updated treatment guidelines for each indication, and treatment should only be initiated after careful assessment of benefit and risk given the local prevalence of resistance and where preferred regimens are not indicated. Missed dose: if 12 hours or less have passed, take it as soon as possible and take the next dose at the regularly scheduled time; if more than 12 hours have passed, wait until the next scheduled dose. Elderly: no dose adjustment required, but particular caution is recommended because of the risk of cardiac arrhythmia and torsade de pointes. Hepatic impairment: no dose adjustment in mild (Child-Pugh A) or moderate (Child-Pugh B) impairment; no data in severe impairment (Child-Pugh C), so administer with caution. §4.5 was not included in this bundle and §4.8 is marked truncated at the source-fetch limit.
Paediatric dose
Route: Oral (powder for oral suspension)
Frequency: Single daily dose
Max: The daily dose should not exceed the adult daily dose of 500 mg, with the exception of the 1-day (single dose) treatment course for acute bacterial otitis media for which the maximum total dose of 1500 mg should not be exceeded. The maximum recommended total dose for any treatment in paediatric patients weighing less than 45 kg is 1500 mg, except for the 5-day regimen for acute streptococcal tonsillitis and pharyngitis
Paediatric patients aged 6 months and older weighing less than 45 kg, by indication (multiple per-kg regimens are stated, so no single per-kg figure is recorded here). 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 followed by 5 mg/kg/day on days 2-5. Acute bacterial otitis media: a single dose of 30 mg/kg, or 10 mg/kg/day for 3 days, or 10 mg/kg on day 1 followed by 5 mg/kg/day on days 2-5. Acute streptococcal tonsillitis and pharyngitis: 20 mg/kg/day for 3 days, or 12 mg/kg/day for 5 days. Safety and efficacy have not been established in children under 6 months of age for any indication, and there is no relevant use for acute exacerbations of chronic bronchitis in paediatric patients. The SPC carries weight-banded maximum daily dose and volume tables for the 20 mg/mL and 40 mg/mL suspensions. Verify against a children's formulary.
Dose adjustments
Renal
No dose adjustment is required in patients with GFR 10 mL/min or greater. In patients with GFR below 10 mL/min azithromycin should be administered with caution.
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.
Contraindications
Hypersensitivity to the active substance, erythromycin, any macrolide or ketolide antibiotic, or to any of the excipients
Side effects
Diarrhoea, headache, vomiting, abdominal pain, nausea and abnormal laboratory test values (most commonly reported)
Anaphylactic reactions, hypersensitivity and angioedema
Torsade de pointes, arrhythmia including ventricular tachycardia, and ECG QT prolongation
Pseudomembranous colitis and pancreatitis
Hepatic failure; severe cutaneous adverse reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, DRESS and acute generalised exanthematous pustulosis
Interactions
Other active substances known to prolong the QT interval — increased risk of ventricular arrhythmias including torsade de pointes; use azithromycin with caution (stated in SPC §4.4, which cross-refers to §4.5; §4.5 itself was not retrieved in this bundle)
Clinical monograph
How it works
It binds the bacterial 50S ribosomal subunit, inhibiting protein synthesis, and is bacteriostatic against susceptible organisms with notable activity against atypical pathogens.
Prescribing in practice
It can prolong the QT interval, so use caution in those with existing QT prolongation, electrolyte disturbance, or taking other QT-prolonging drugs.
Use cautiously in significant hepatic impairment and discontinue if signs of liver dysfunction develop.
As a macrolide it interacts with several drugs and, like other antibiotics, carries a risk of Clostridioides difficile-associated diarrhoea.
Monitoring
Routine monitoring is not usually required for short courses; consider ECG and electrolytes where cardiac risk factors exist and monitor for hepatic or diarrhoeal adverse effects.
Counselling the patient
Complete the full prescribed course even if you feel better.
Report a fast or irregular heartbeat, fainting, or severe or persistent diarrhoea.
Tell the prescriber about all your other medicines.
Evidence & guidelines
Azithromycin is well established for specific indications in UK practice; macrolide use is guided by local microbiology and resistance considerations.
Reference: NICE CG191 (Pneumonia); BASHH Chlamydia Guidelines; BTS CAP Guidelines; 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.