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# Azithromycin
## Overview
Azithromycin is an azalide antibiotic (a subclass of macrolides) that inhibits protein synthesis by binding to the 50S ribosomal subunit. It is characterized by a long half-life (approx. 68 hours) and high tissue penetration.
## Primary Indications
* Community-acquired pneumonia (CAP)
* Pharyngitis/Tonsillitis (group A streptococcal alternative)
* Acute bacterial exacerbation of chronic bronchitis
* Uncomplicated skin/soft tissue infections
* Chlamydia trachomatis (genital infections)
* *Mycobacterium avium* complex (MAC) prophylaxis/treatment
* Acute otitis media (AOM)
## Adult Dosing
* **Respiratory/Skin infections:** 500 mg on day 1, followed by 250 mg once daily on days 2–5.
* **Chlamydia:** 1 gram orally as a single dose.
* **MAC Prophylaxis:** 1,200 mg orally once weekly.
* *Note: Dosing varies based on local susceptibility patterns and specific infection severity.*
## Pediatric Dosing
* **AOM:** 30 mg/kg as a single dose OR 10 mg/kg once daily for 3 days.
* **CAP/Pharyngitis:** 10 mg/kg on day 1 (max 500 mg), followed by 5 mg/kg once daily on days 2–5 (max 250 mg).
* *Note: Safety and efficacy have not been established in infants <6 months of age.*
## Dose Adjustments
* **Renal Impairment:** No specific adjustments required for CrCl ≥10 mL/min. Use caution if CrCl <10 mL/min.
* **Hepatic Impairment:** Use with caution; the drug is primarily eliminated via the liver.
## Contraindications
* Hypersensitivity to azithromycin, erythromycin, or any macrolide/ketolide antibiotic.
* History of cholestatic jaundice or hepatic dysfunction associated with prior azithromycin use.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, abdominal pain.
* **Serious:** QT interval prolongation (risk of Torsades de Pointes), hepatotoxicity, *Clostridioides difficile*-associated diarrhea (CDAD), severe hypersensitivity reactions (DRESS, SJS/TEN).
## Key Drug Interactions
* **QT Prolonging Agents:** Increased risk of life-threatening arrhythmias.
* **Warfarin:** May potentiate anticoagulant effects; monitor INR closely.
* **Digoxin:** May increase serum concentration (leads to potential toxicity).
* **Statins:** Increased risk of myopathy/rhabdomyolysis.
## Monitoring
* **Cardiac:** ECG monitoring recommended if the patient has risk factors for QT prolongation or severe electrolyte disturbances (hypokalemia/hypomagnesemia).
* **Hepatic:** Monitor for signs of jaundice or elevated LFTs if treatment is prolonged.
* **Clinical:** Monitor for signs of superinfection or *C. difficile* diarrhea.
## Clinical Pearls
* **Administration:** May be taken with or without food. However, taking with food may reduce GI side effects.
* **Long Half-life:** The extended half-life allows for shorter courses of therapy, which can improve adherence.
* **Resistance:** Macrolide resistance is increasing globally; do not use as empiric monotherapy where local resistance rates for *S. pneumoniae* are high (>25%).
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**Educational Disclaimer:** This information is for educational purposes only. Prescribing practices and local resistance patterns vary significantly. Always verify doses, contraindications, and pediatric safety against current institutional protocols and the most recent FDA-approved product labeling (Package Insert) before prescribing or administering medication.
