What is the dosage and treatment duration for Azithromycin (a macrolide antibiotic)?

Azithromycin Dosing and Treatment Duration

Standard Adult Dosing Regimens

For most respiratory tract infections in adults, azithromycin should be dosed as 500 mg on day 1 followed by 250 mg once daily on days 2-5, or alternatively 500 mg once daily for 3 days. 1

Infection-Specific Dosing

Respiratory Tract Infections:

• Community-acquired pneumonia (mild): 500 mg day 1, then 250 mg daily days 2-5 1
• Acute bacterial exacerbations of COPD: Either 500 mg daily for 3 days OR 500 mg day 1, then 250 mg daily days 2-5 1
• Acute bacterial sinusitis: 500 mg daily for 3 days 1
• Pharyngitis/tonsillitis (second-line): 500 mg day 1, then 250 mg daily days 2-5 1

Sexually Transmitted Infections:

• Non-gonococcal urethritis/cervicitis (Chlamydia): Single 1 gram dose 1, 2
• Gonococcal urethritis/cervicitis: Single 2 gram dose (must be combined with ceftriaxone 1g IM/IV) 1, 2
• Chancroid: Single 1 gram dose 1

Skin and Soft Tissue Infections (uncomplicated): 500 mg day 1, then 250 mg daily days 2-5 1

Pediatric Dosing (≥6 months)

For acute otitis media and community-acquired pneumonia, use 10 mg/kg on day 1 (maximum 500 mg) followed by 5 mg/kg daily on days 2-5 (maximum 250 mg). 1

Alternative Pediatric Regimens

Acute Otitis Media:

• 5-day regimen: 10 mg/kg day 1, then 5 mg/kg days 2-5 1
• 3-day regimen: 10 mg/kg daily for 3 days 1
• 1-day regimen: 30 mg/kg as single dose 1

Acute Bacterial Sinusitis: 10 mg/kg daily for 3 days 1

Pharyngitis/Tonsillitis: 12 mg/kg once daily for 5 days (required due to higher recurrence rates with standard dosing) 1, 3

Chronic Maintenance Therapy

Bronchiectasis with ≥3 exacerbations/year:

• Preferred starting dose: 500 mg three times weekly OR 250 mg daily 2
• Alternative: 250 mg three times weekly if gastrointestinal side effects occur at higher dose 2
• Duration: Minimum 6-12 months to assess efficacy 2

Cystic Fibrosis with chronic Pseudomonas aeruginosa:

• 250 mg daily OR 250-500 mg three times weekly 2
• Continue long-term if beneficial 2

Asthma (severe, uncontrolled):

• 500 mg three times weekly OR 250 mg daily 2
• Trial for 6-12 months; discontinue if no benefit 2

Disseminated MAC in HIV/AIDS:

• Continue full therapeutic doses lifelong as secondary prophylaxis 2
• Typical dose: 500 mg daily in combination with ethambutol 2

Critical Dosing Considerations

Renal Impairment:

• No adjustment needed for GFR 10-80 mL/min 1
• Exercise caution with GFR <10 mL/min (35% increase in AUC) 1

Hepatic Impairment:

• No specific dosing recommendations available; use with caution 1

Food Effects:

• Can be taken with or without food for tablets 1
• Large meals may reduce absorption by up to 50% 4

Common Pitfalls

Never use azithromycin as monotherapy for MAC disease - this rapidly selects for macrolide-resistant strains with cross-resistance to all macrolides 2

Screen for QTc prolongation before initiating chronic therapy - contraindicated if QTc >450 ms (men) or >470 ms (women) 2

For pertussis in infants <1 month: Use 10 mg/kg daily for 5 days and monitor for infantile hypertrophic pyloric stenosis 2

Avoid aluminum/magnesium antacids - these reduce azithromycin absorption when taken simultaneously 2

For gonococcal infections, azithromycin must be combined with ceftriaxone - never use as monotherapy due to resistance 2