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# Azithromycin
## Overview
Azithromycin is a macrolide antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit. It has a broad spectrum of activity against many gram-positive and gram-negative bacteria, as well as atypical pathogens.
## Primary Indications
* Acute bacterial exacerbations of chronic obstructive pulmonary disease (COPD)
* Community-acquired pneumonia (CAP)
* Streptococcal pharyngitis (alternative to penicillin)
* Uncomplicated skin and skin structure infections
* Genital ulcer disease due to *Chlamydia trachomatis*
* Nongonococcal urethritis/cervicitis due to *Chlamydia trachomatis*
* Prophylaxis and treatment of disseminated *Mycobacterium avium* complex (MAC) disease
## Adult Dosing
* **Acute bacterial exacerbations of COPD:** 500 mg once daily for 3 days.
* **CAP:** 500 mg on day 1, followed by 250 mg once daily on days 2-5.
* **Streptococcal pharyngitis:** 500 mg once daily for 3 days OR 1 gram on day 1, followed by 500 mg once daily on days 2-5.
* **Uncomplicated skin and skin structure infections:** 500 mg on day 1, followed by 250 mg once daily on days 2-5.
* ***Chlamydia trachomatis* cervical/urethral infections:** 1 gram orally once.
* **MAC prophylaxis/treatment:** Dosing varies depending on indication and concomitant agents. Consult specific guidelines.
## Pediatric Dosing
Dosing is weight-based and depends on the indication. Exact dosing regimens should be confirmed with current pediatric guidelines or product labeling. Common indications include otitis media, CAP, and pharyngitis. Maximum doses should be adhered to.
## Dose Adjustments
No dose adjustment is typically needed in renal impairment. Use with caution in severe hepatic impairment.
## Contraindications
* Hypersensitivity to azithromycin, erythromycin, any macrolide, or any component of the formulation.
* History of cholestatic jaundice or hepatic dysfunction associated with prior azithromycin use.
## Adverse Effects
Common: Diarrhea, nausea, abdominal pain, vomiting.
Serious: *Clostridioides difficile*-associated diarrhea, hepatotoxicity (including cholestatic hepatitis and hepatic necrosis), QTc interval prolongation, severe allergic reactions (including Stevens-Johnson syndrome and toxic epidermal necrolysis).
## Key Drug Interactions
* **Theophylline:** Monitor for potential toxicity.
* **Warfarin:** Monitor INR. Azithromycin has been reported to potentiate warfarin effects.
* **Antacids containing magnesium or aluminum:** May decrease azithromycin absorption; separate administration by at least 2 hours.
* **Drugs that prolong QTc interval:** Increased risk of arrhythmias.
## Monitoring
* Signs and symptoms of infection.
* Liver function tests (LFTs) if symptoms of hepatic dysfunction arise or with prolonged therapy.
* INR if co-administered with warfarin.
* ECG for QTc interval prolongation in patients with risk factors.
## Clinical Pearls
Azithromycin has a long half-life, allowing for once-daily dosing and shorter treatment courses for some infections. It is often prescribed for its convenience and broad spectrum of activity. Be aware of the potential for *C. difficile* infection.
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***Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information, product labeling, and relevant guidelines for complete and up-to-date guidance before making therapeutic decisions. Drug information can change frequently.*
