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# Azithromycin
## Overview
Azithromycin is a macrolide antibiotic used to treat a variety of bacterial infections. It inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit.
## Primary Indications
* **Respiratory Tract Infections:** Community-acquired pneumonia (CAP), acute exacerbations of chronic bronchitis, pharyngitis/tonsillitis (when penicillin is not an option).
* **Skin and Soft Tissue Infections:** Uncomplicated skin and skin structure infections.
* **Genital Ulcer Diseases:** Chancroid.
* **Disseminated Mycobacterium avium complex (MAC) infections:** Prophylaxis and treatment in patients with advanced HIV.
* **Alternative for:** Acute otitis media, sinusitis, gonorrhea, chlamydia.
## Adult Dosing
* **CAP:** 500 mg on day 1, then 250 mg once daily on days 2-5.
* **Acute exacerbations of chronic bronchitis:** 500 mg once daily for 3 days.
* **Pharyngitis/Tonsillitis:** 500 mg on day 1, then 250 mg once daily on days 2-5.
* **Uncomplicated skin and skin structure infections:** 500 mg on day 1, then 250 mg once daily on days 2-5.
* **Chancroid:** Single dose of 1 gram.
* **Disseminated MAC Prophylaxis (HIV patients CD4 < 50):** 1.2 grams once weekly.
* **Disseminated MAC Treatment (HIV patients):** 500 mg twice daily for 7 days, then 500 mg once daily. Often given in combination with ethambutol. *Dosage adjustment may be necessary based on local guidelines and susceptibility.*
## Pediatric Dosing
* **CAP:** 10 mg/kg on day 1 (max 500 mg), then 5 mg/kg once daily on days 2-5 (max 250 mg daily).
* **Acute otitis media:** 10 mg/kg on day 1 (max 500 mg), then 5 mg/kg once daily on days 2-5 (max 250 mg daily).
* **Pharyngitis/Tonsillitis:** 12 mg/kg once daily for 5 days (max 500 mg daily).
* *Dosing for other indications, especially MAC, may vary and should be confirmed with current guidelines.*
## Dose Adjustments
No specific dose adjustment is recommended for renal or hepatic impairment. However, caution is advised in severe hepatic impairment.
## Contraindications
* Hypersensitivity to azithromycin, erythromycin, or any macrolide antibiotic.
## Adverse Effects
* **Common:** Diarrhea, nausea, abdominal pain, vomiting.
* **Less Common:** Headache, dizziness, rash, elevated liver enzymes.
* **Rare but Serious:** QT prolongation, torsades de pointes, severe allergic reactions (anaphylaxis, Stevens-Johnson syndrome), C. difficile-associated diarrhea.
## Key Drug Interactions
* **Theophylline:** May increase theophylline levels. Monitor clinical response and adjust theophylline dose if needed.
* **Warfarin:** May increase INR. Monitor INR closely.
* **Antacids containing magnesium or aluminum:** May decrease azithromycin absorption. Administer azithromycin at least 1 hour before or 2 hours after antacids.
* **Drugs that prolong QT interval (e.g., some antiarrhythmics, antipsychotics):** Increased risk of QT prolongation and torsades de pointes. Use with caution or avoid.
* **Digoxin:** May increase digoxin levels. Monitor digoxin levels and clinical signs of toxicity.
## Monitoring
* Monitor for signs and symptoms of hypersensitivity reactions.
* Monitor for signs of C. difficile-associated diarrhea.
* In patients with prolonged QT intervals or taking other QT-prolonging drugs, consider ECG monitoring.
* Monitor liver function tests periodically, especially in patients with existing hepatic disease or those on long-term therapy.
## Clinical Pearls
* Azithromycin has a long half-life, allowing for once-daily dosing and shorter treatment courses for some indications.
* It is often used as an alternative for patients allergic to penicillin.
* Ensure adequate hydration, especially in pediatric patients, to prevent concentration of urine and potential crystallization if oral suspension is used.
* Oral suspensions should be reconstituted according to instructions and stored properly. Discard unused suspension after the recommended storage period.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant guidelines for complete details, including contraindications, warnings, precautions, and adverse effects, before prescribing or administering any medication.
