Makindo Medical Notes

⚡ 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)

🔄 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