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# Azithromycin
## Overview
Azithromycin is a macrolide antibiotic that inhibits bacterial protein synthesis. It has broad-spectrum activity against many Gram-positive and Gram-negative bacteria, as well as atypical organisms.
## Primary Indications
* **Respiratory Tract Infections:** Acute exacerbations of COPD, community-acquired pneumonia, pharyngitis/tonsillitis (Streptococcus pyogenes).
* **Skin and Soft Tissue Infections:** Uncomplicated skin and skin structure infections.
* **Sexually Transmitted Infections:** Chlamydia trachomatis, Neisseria gonorrhoeae (uncomplicated urogenital, rectal, pharyngeal infections).
* **Mycobacterium avium complex (MAC) prophylaxis and treatment** in patients with advanced HIV infection.
* **Prophylaxis of pertussis.**
## Adult Dosing
* **Community-Acquired Pneumonia:** 500 mg on day 1, followed by 250 mg once daily on days 2-5. (Total 1.5 g)
* **Acute Exacerbations of COPD:** 500 mg once daily for 3 days. (Total 1.5 g)
* **Pharyngitis/Tonsillitis:** 500 mg on day 1, followed by 250 mg once daily on days 2-5. (Total 1.5 g)
* **Uncomplicated Skin and Skin Structure Infections:** 500 mg on day 1, followed by 250 mg once daily on days 2-5. (Total 1.5 g)
* **Chlamydia trachomatis (uncomplicated urogenital, rectal, pharyngeal):** 1 gram (1000 mg) as a single dose.
* **Neisseria gonorrhoeae (uncomplicated urogenital, rectal, pharyngeal):** 2 grams (2000 mg) as a single dose (often given with ceftriaxone).
* **MAC Prophylaxis:** 1200 mg once weekly.
* **MAC Treatment:** 600 mg once daily, usually in combination with ethambutol.
## Pediatric Dosing
Dosing is weight-based and depends on the indication. Exact dosing depends on local protocol.
* **Acute Otitis Media:** 10 mg/kg on day 1 (maximum 500 mg), followed by 5 mg/kg once daily on days 2-5 (maximum 250 mg/day). (Total 50 mg/kg)
* **Community-Acquired Pneumonia:** 10 mg/kg on day 1 (maximum 500 mg), followed by 5 mg/kg once daily on days 2-5 (maximum 250 mg/day). (Total 50 mg/kg)
* **Streptococcal Pharyngitis:** 12 mg/kg once daily for 5 days (maximum 500 mg/day). (Total 60 mg/kg)
* **MAC Prophylaxis:** 20 mg/kg once weekly (maximum 1200 mg/week).
* **MAC Treatment:** Varies; typically 10-20 mg/kg/day divided into 1-2 doses (maximum 600 mg/day), in combination therapy.
## Dose Adjustments
No dose adjustment is required for renal impairment. Use with caution in severe hepatic impairment.
## Contraindications
* Hypersensitivity to azithromycin, erythromycin, any macrolide antibiotic, or any component of the formulation.
## Adverse Effects
* **Common:** Diarrhea, nausea, abdominal pain, vomiting, rash.
* **Serious:** QT prolongation, torsades de pointes, Clostridioides difficile-associated diarrhea, hepatotoxicity (including cholestatic hepatitis and hepatic necrosis), severe allergic reactions (including anaphylaxis and Stevens-Johnson syndrome).
## Key Drug Interactions
* **CYP3A4 Substrates:** Azithromycin is a weak inhibitor of CYP3A4. Monitor for increased concentrations of drugs metabolized by CYP3A4 (e.g., warfarin, cyclosporine, theophylline, certain calcium channel blockers, statins).
* **Digoxin:** Azithromycin may increase digoxin levels. Monitor digoxin levels and clinical signs of toxicity.
* **Antacids containing aluminum or magnesium:** May decrease azithromycin absorption. Separate administration by at least 2 hours.
* **Drugs that prolong the QT interval:** Increased risk of QT prolongation and torsades de pointes (e.g., antiarrhythmics, antipsychotics, certain antibiotics).
## Monitoring
* Monitor for signs and symptoms of hypersensitivity reactions.
* Monitor for signs and symptoms of Clostridioides difficile-associated diarrhea.
* Monitor liver function tests (LFTs) if therapy is prolonged or in patients with pre-existing liver disease.
* Monitor for signs of QT prolongation, especially in patients with risk factors.
* Monitor for signs of drug interactions.
## Clinical Pearls
* Azithromycin has a long half-life, allowing for once-daily dosing and shorter treatment courses for some indications.
* Can be taken with or without food, though administration with food may improve absorption for oral suspension.
* For MAC treatment and prophylaxis, azithromycin is a cornerstone agent, typically used in combination.
* Use of azithromycin for gonorrhea may be associated with increasing resistance. Current guidelines recommend specific combination therapy.
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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 for azithromycin and consider individual patient factors before making treatment decisions. Local protocols and guidelines may influence dosing and management strategies.*
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