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# Azithromycin ## Overview Azithromycin is a macrolide antibiotic used to treat a variety of bacterial infections. ## Primary Indications * **Respiratory Tract Infections:** Acute bacterial exacerbations of COPD, community-acquired pneumonia, strep pharyngitis, acute otitis media. * **Skin and Soft Tissue Infections:** Uncomplicated skin and skin structure infections. * **Sexually Transmitted Infections:** Chlamydia trachomatis (genital, rectal, pharyngeal), chancroid. * **Other:** Prophylaxis for MAC (Mycobacterium avium complex) in patients with advanced HIV. ## Adult Dosing * **Community-Acquired Pneumonia:** 500 mg on day 1, followed by 250 mg once daily on days 2-5. * **Acute Bacterial Exacerbations of COPD:** 500 mg once daily for 3 days. * **Acute Otitis Media:** 10 mg/kg on day 1 (max 500 mg), followed by 5 mg/kg once daily on days 2-5 (max 250 mg/day). * **Strep Pharyngitis:** 500 mg once daily for 5 days. * **Chlamydia trachomatis (uncomplicated urethral, cervical, rectal):** 1 gram orally as a single dose. * **Chancroid:** 1 gram orally as a single dose. * **MAC Prophylaxis:** 1.2 grams once weekly. ## Pediatric Dosing Dosing in children often depends on weight and indication. Consult specific pediatric guidelines or product information for exact dosing. * **Acute Otitis Media:** 10 mg/kg on day 1 (max 500 mg), followed by 5 mg/kg once daily on days 2-5 (max 250 mg/day). * **Community-Acquired Pneumonia:** 10 mg/kg on day 1 (max 500 mg), followed by 5 mg/kg once daily on days 2-5 (max 250 mg/day). * **Strep Pharyngitis:** 12 mg/kg once daily for 5 days (max 500 mg/day). ## Dose Adjustments No dose adjustment is generally required for hepatic or renal impairment, although caution is advised in severe renal impairment. ## Contraindications * Hypersensitivity to azithromycin, erythromycin, or any macrolide or ketolide antibiotic. * History of cholestatic jaundice/hepatic dysfunction associated with prior azithromycin use. ## Adverse Effects * **Common:** Diarrhea, nausea, abdominal pain, vomiting. * **Less Common:** Dizziness, headache, rash, dysgeusia. * **Serious:** QT prolongation (leading to torsades de pointes), severe hypersensitivity reactions (including anaphylaxis and Stevens-Johnson syndrome), Clostridioides difficile-associated diarrhea, hepatotoxicity. ## Key Drug Interactions * **Theophylline:** Monitor theophylline levels. * **Warfarin:** Monitor INR. * **Antacids (aluminum/magnesium):** May decrease azithromycin absorption; separate administration by at least 2 hours. * **CYP3A4 Substrates (e.g., cyclosporine, digoxin, certain statins):** Monitor for potential toxicity. Azithromycin is a weak inhibitor of CYP3A4. * **Drugs that prolong QT interval:** Increased risk of cardiac arrhythmias. ## Monitoring * Monitor for signs and symptoms of hypersensitivity reactions. * Monitor for signs of C. difficile infection (diarrhea). * Monitor for signs of hepatotoxicity (jaundice, elevated liver enzymes) especially with prolonged or repeated courses. * Monitor for effectiveness of treatment. ## Clinical Pearls * Azithromycin has a long half-life,