Azithromycin Macrolide Antibiotic Bacterial infection Respiratory tract infection Pneumonia Bronchitis Pharyngitis Tonsillitis Sinusitis Otitis media

1.1 Pharmacological Mechanism

• Superior tissue distribution: Concentrates heavily in respiratory tract, tonsils, sinuses, middle ear and genital tissues, tissue drug levels far exceed plasma concentration.
• Ultra-long elimination half-life (≈68 hours), supporting short-course treatment (1-day, 3-day, 5-day regimens) with once-daily administration.
• Acid-resistant structure, stable oral absorption; food causes mild absorption interference, strict fasting is not mandatory.
• Lower gastrointestinal irritation than erythromycin; minimal liver enzyme induction, fewer drug-drug interactions.

1.2 Clinical Indications (Mild to Moderate Susceptible Bacterial Infections)

1. Respiratory tract infections: Community-acquired pneumonia, acute bronchitis, chronic bronchitis acute exacerbation, bacterial sinusitis, otitis media, pharyngitis, tonsillitisDailyMed.
2. Atypical pathogen infections: Mycoplasma pneumoniae, Chlamydia pneumoniae respiratory infections.
3. Genitourinary infections: Urethritis, cervicitis caused by Chlamydia trachomatis; single-dose therapy for uncomplicated genital chlamydia infection.
4. Skin & soft tissue infections: Mild uncomplicated bacterial skin infections.
5. Limitation of use: Ineffective for viral colds, influenza and fungal infections; only prescribed for confirmed bacterial infections to avoid drug-resistant bacteria.

1.3 Population & Formulation Advantages

2. Specification & Regulatory Parameters

2.1 Chemical & Physical Parameters

• Chemical Name: Azithromycin (C₃₈H₇₂N₂O₁₂)
• Molecular Weight: 748.99
• API Appearance: White or off-white crystalline powder; slightly soluble in water, soluble in methanol and ethanolDailyMed.
• Tablet Appearance: White biconvex film-coated tablets with engraved strength marking; dispersible tablets dissolve rapidly in warm water.
• Dry Suspension: White powder before reconstitution; milky uniform suspension after mixing with purified water, pH 6.0–8.0.
• Storage Condition: Sealed, stored below 25°C in cool & dry place; reconstituted oral suspension must be refrigerated and used within 10 days.

2.2 Main Dosage Forms & Standard Specifications

1. Azithromycin Film-coated Tablets: 125mg, 250mg, 500mg
2. Azithromycin Dispersible Tablets: 125mg, 250mg
3. Azithromycin Dry Suspension: 100mg/5mL, 200mg/5mL
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2.3 Standard Dosing Rules

• Adults (respiratory infection): 500mg single dose on Day 1, 250mg once daily Day 2–5; 3-day regimen: 500mg once daily for 3 consecutive days.
• Chlamydia genital infection: Single oral dose of 1000mg.
• Pediatrics (≥6 months old): 10mg/kg once daily on Day 1, followed by 5mg/kg daily Day 2–5; acute otitis media single-dose 30mg/kg.
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2.4 Contraindications & Compatibility Rules

1. Absolute Contraindication: Patients with hypersensitivity to macrolide antibiotics (azithromycin, erythromycin, clarithromycin).
2. Cautious Use: Hepatic impairment, severe renal dysfunction, history of QT interval prolongation, arrhythmia risk groups.
3. Drug Compatibility Restrictions: Do not co-administer with aluminum/magnesium-containing antacids (separate administration by ≥2 hours); avoid combined use with QT-prolonging agents (cisapride, amiodarone) to reduce arrhythmia risk.
4. Administration Restriction: Prohibit long-term blind use; stop medication immediately once bacterial infection symptoms resolve.

3. Unified Quality Standards

3.1 Executive Pharmacopoeia Standards