⚡ Unlike erythromycin and clarithromycin, azithromycin does not inhibit CYP3A4. This makes it less prone to clinically significant drug–drug interactions.

📖 About

Always check the BNF link here.

💊 Widely used macrolide antibiotic, often as an alternative in penicillin allergy.
🦠 Particularly useful for respiratory tract infections and atypical pathogens.
📌 Long half-life allows for short-course or single-dose regimens.

⚡ Properties

✅ Excellent tissue penetration (except CSF).
⏱️ Long half-life (2–4 days) → once-daily dosing or single high-dose administration.
⚠️ 15-lactone macrolide ring → does not inhibit CYP3A4, unlike erythromycin/clarithromycin.

🔬 Mechanism of Action

Binds to the 50S subunit of the bacterial ribosome.
Inhibits bacterial protein synthesis → bacteriostatic (can be bactericidal at high concentrations).
📈 Broader activity against Gram-negative organisms compared with erythromycin, but slightly less active against Gram-positive.

🩺 Indications & Dosing (verify in BNF/datasheet)

Alternative in penicillin allergy.
🌬️ Respiratory infections – bronchitis, pneumonia, atypical pathogens (Mycoplasma, Chlamydophila, Legionella).
💢 Whooping cough (pertussis).
🧫 Chlamydial infections (urethritis/cervicitis).
💧 Campylobacter enteritis.

💊 Dosing – Azithromycin (verify with BNF/datasheet)

Indication	Details
📋 Standard Course	Azithromycin • 250–500 mg PO OD × 3 days
🧬 Chlamydial urethritis / cervicitis	Azithromycin • 1 g PO single dose

🔄 Interactions

Does not inhibit CYP3A4 → fewer interactions compared with other macrolides.
⚠️ Still caution with QT-prolonging drugs (e.g. amiodarone, antipsychotics, fluoroquinolones).

⚠️ Cautions

💔 QT prolongation or concurrent QT-prolonging drugs.
🧬 Acute porphyria.
📉 Severe hepatic impairment.

🚫 Contraindications

Known hypersensitivity to macrolides.
Severe liver disease/failure.

💥 Side Effects

🤢 GI upset: nausea, vomiting, diarrhoea, dyspepsia (less common than with erythromycin).
🌡️ Skin rash, hypersensitivity reactions.
🫀 QT prolongation, arrhythmias (torsades de pointes).
🧠 Headache, dizziness, rarely convulsions.
🫁 Hepatotoxicity: cholestatic jaundice, hepatitis, liver failure (rare).
🩸 Rare: interstitial nephritis, haemolytic anaemia.

📑 References

BNF: Azithromycin
UK NICE guidance: Pneumonia & Chlamydial infection

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Azithromycin 💊