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# Azithromycin
## Overview
Azithromycin is a macrolide antibiotic effective against a wide range of bacteria. It inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit.
## Primary Indications
* **Respiratory Tract Infections:** Community-acquired pneumonia (CAP), acute exacerbations of COPD, pharyngitis/tonsillitis (caused by *Streptococcus pyogenes*).
* **Skin and Soft Tissue Infections:** Uncomplicated skin and skin structure infections.
* **Genital Ulcer Disease:** Chancroid.
* **Disseminated *Mycobacterium avium* Complex (MAC) Infections:** Prophylaxis and treatment in patients with advanced HIV.
* **Other:** Acute otitis media, sinusitis.
## Adult Dosing
* **CAP:** 500 mg on day 1, then 250 mg daily on days 2-5.
* **Acute bacterial exacerbations of COPD:** 500 mg daily for 3 days.
* **Pharyngitis/Tonsillitis:** 500 mg on day 1, then 250 mg daily on days 2-5.
* **Uncomplicated Skin and Soft Tissue Infections:** 500 mg on day 1, then 250 mg daily on days 2-5, OR 1000 mg as a single dose (alternative regimen).
* **Chancroid:** 1 g as a single oral dose.
* **MAC Prophylaxis:** 1.2 g once weekly.
* **MAC Treatment:** 600 mg once daily, often in combination with other agents. The duration depends on clinical response and culture results.
## Pediatric Dosing
Dosing varies by indication and age/weight. Consult specific pediatric guidelines or product labeling for precise calculations.
* **Acute Otitis Media:** 10 mg/kg on day 1 (maximum 500 mg), then 5 mg/kg daily on days 2-5 (maximum 250 mg/day).
* **CAP:** 10 mg/kg on day 1 (maximum 500 mg), then 5 mg/kg daily on days 2-5 (maximum 250 mg/day).
* **Streptococcal Pharyngitis:** 12 mg/kg once daily for 5 days (maximum 500 mg/day).
## Dose Adjustments
No dose adjustment is typically required for hepatic or renal impairment, though caution is advised in severe hepatic disease.
## Contraindications
* Hypersensitivity to azithromycin, erythromycin, other macrolides, or any component of the formulation.
* History of cholestatic jaundice/hepatic dysfunction associated with prior azithromycin use.
## Adverse Effects
* **Common:** Diarrhea, nausea, abdominal pain, vomiting.
* **Serious:** QT interval prolongation, *Clostridioides difficile*-associated diarrhea, hepatotoxicity (including cholestatic hepatitis and hepatic failure), angioedema, anaphylaxis, Stevens-Johnson syndrome.
## Key Drug Interactions
* **QTc-prolonging agents:** Increased risk of ventricular arrhythmias.
* **Warfarin:** Increased INR and bleeding risk. Monitor INR closely.
* **Theophylline:** Potential for increased theophylline levels.
* **Antacids containing magnesium/aluminum:** May decrease azithromycin absorption. Separate administration by at least 2 hours.
* **Digoxin:** Azithromycin may increase digoxin levels.
## Monitoring
* Assess for signs and symptoms of hypersensitivity reactions.
* Monitor for diarrhea, especially if severe or persistent, for *C. difficile* infection.
* Consider LFTs in patients with pre-existing liver disease or if signs/symptoms of hepatotoxicity develop.
* Monitor INR in patients taking concomitant warfarin.
* ECG monitoring may be considered in patients with risk factors for QT prolongation.
## Clinical Pearls
* Azithromycin has a long half-life, allowing for a short course of therapy with a convenient dosing regimen for many indications.
* It concentrates well in tissues, which contributes to its efficacy and prolonged activity.
* For strep throat, azithromycin is an alternative to penicillin but penicillin is preferred if rheumatic fever is a concern.
* Ensure adequate hydration and avoid administration with antacids containing magnesium/aluminum to optimize absorption.
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***Educational Disclaimer:** This information is intended for healthcare professionals. It is essential to consult the most current prescribing information (package insert) and relevant clinical guidelines for complete details, including comprehensive safety information, and to confirm dosing and indications prior to patient management. Local protocols may impact prescribing decisions.***
