What is the recommended dose of Azithromycin (macrolide antibiotic) for treating common bacterial infections?

Azithromycin Dosing for Common Bacterial Infections

For most common bacterial infections in adults, azithromycin should be dosed as 500 mg on day 1, followed by 250 mg once daily on days 2-5, for a total 5-day course. 1

Adult Dosing by Indication

Respiratory Tract Infections

Community-Acquired Pneumonia (mild severity):

• 500 mg as a single dose on Day 1, followed by 250 mg once daily on Days 2-5 1
• Total course: 1.5 grams over 5 days 1

Acute Bacterial Exacerbations of COPD:

• Option 1 (preferred for simplicity): 500 mg once daily for 3 days 1
• Option 2: 500 mg on Day 1, then 250 mg once daily on Days 2-5 1

Acute Bacterial Sinusitis:

• 500 mg once daily for 3 days 1

Pharyngitis/Tonsillitis (second-line therapy):

• 500 mg on Day 1, then 250 mg once daily on Days 2-5 1

Skin and Soft Tissue Infections

Uncomplicated skin/skin structure infections:

• 500 mg on Day 1, followed by 250 mg once daily on Days 2-5 1

Sexually Transmitted Infections

Non-gonococcal urethritis and cervicitis:

• Single 1-gram dose 1

Gonococcal urethritis and cervicitis:

• Single 2-gram dose 1

Genital ulcer disease (chancroid):

• Single 1-gram dose 1

Pediatric Dosing (Age 6 months and above)

Acute Otitis Media

5-Day Regimen (preferred):

• Day 1: 10 mg/kg as a single dose 1
• Days 2-5: 5 mg/kg once daily 1

3-Day Regimen:

• 10 mg/kg once daily for 3 days 1

1-Day Regimen:

• 30 mg/kg as a single dose 1

Community-Acquired Pneumonia

Standard regimen:

• Day 1: 10 mg/kg as a single dose 1
• Days 2-5: 5 mg/kg once daily 1

For hospitalized children with atypical pneumonia:

• Intravenous: 10 mg/kg on days 1 and 2 of therapy 2

Acute Bacterial Sinusitis

• 10 mg/kg once daily for 3 days 1

Pharyngitis/Tonsillitis (Age 2 years and above)

• 12 mg/kg once daily for 5 days 1

Special Populations

Immunocompromised Patients

For babesiosis in immunocompromised patients:

• Higher doses of 600-1000 mg per day may be used 3

Renal Impairment

• No dosage adjustment needed for GFR 10-80 mL/min 1
• Exercise caution with severe renal impairment (GFR <10 mL/min), as AUC increases by 35% 1

Hepatic Impairment

• No established dosing recommendations; pharmacokinetics not studied in this population 1
• Use with caution 1

Important Clinical Considerations

Administration

• Can be taken with or without food for tablets 1
• Oral suspension can be taken with or without food 1
• Caution: Coadministration with a large meal may reduce absorption by up to 50% 4

Duration and Monitoring

• Clinical improvement should occur within 48-72 hours of starting therapy 2
• If no improvement within this timeframe, reevaluation is necessary 2
• The extended tissue half-life (up to 5 days) allows azithromycin to remain effective for several days after administration ceases 5

Common Pitfalls to Avoid

Underdosing in streptococcal pharyngitis:

• In children with GAS tonsillopharyngitis, 60 mg/kg total course is superior to 30 mg/kg total course 6
• 3-day regimens are inferior to 5-day regimens in children 6
• In adults, 3-day regimens of 500 mg/day show better outcomes than 5-day regimens 6

Re-dosing after vomiting:

• In pediatric patients who vomit within 30 minutes of receiving a 30 mg/kg single dose, re-dosing at the same total dose has been done in clinical studies, though safety data are limited 1

Drug interactions:

• Azithromycin inhibits P-glycoprotein, potentially increasing concentrations of P-gp substrates like cyclosporine 3
• Monitor cyclosporine levels closely in immunocompromised patients 3

Cardiac Safety

• QT prolongation risk exists, particularly when combined with hydroxychloroquine 3
• Avoid combination with other QT-prolonging agents (certain TKIs, arsenic trioxide, antidepressants) 3