What is the typical dose of azithromycin (Zithromax) for a 3-day course?

Azithromycin 3-Day Dosing Regimen

For a 3-day course of azithromycin in adults, the standard dose is 500 mg once daily for 3 consecutive days, providing a total dose of 1.5 grams. 1

Standard Adult 3-Day Regimen

• The recommended dose is 500 mg orally once daily for 3 consecutive days for respiratory tract infections including community-acquired pneumonia, acute bacterial sinusitis, and bronchitis 1
• This 3-day regimen delivers the same total 1.5 gram dose as the traditional 5-day Z-pack (500 mg day 1, then 250 mg days 2-5) and is equally effective 1
• The 3-day course has been validated in multiple clinical trials for community-acquired pneumonia, atypical pneumonia, and acute exacerbations of chronic bronchitis, with cure rates of 95-98% 2, 3, 4

Pediatric 3-Day Dosing

• Children should receive 10 mg/kg once daily for 3 consecutive days (maximum 500 mg per dose) 5
• This pediatric 3-day regimen has demonstrated equivalent efficacy to longer courses of comparator antibiotics for otitis media, respiratory tract infections, and skin/soft tissue infections 5

Key Clinical Advantages

• The 3-day regimen significantly improves adherence compared to longer courses due to simplified once-daily dosing and shorter duration 6
• Azithromycin achieves prolonged therapeutic tissue concentrations (7-10 days) despite the short treatment course due to extensive tissue distribution and slow elimination 6, 3
• Most patients become afebrile within 48 hours of starting treatment 2

Important Administration Considerations

• Separate azithromycin from aluminum- or magnesium-containing antacids by at least 2 hours, as antacids reduce absorption by up to 50% 1
• Azithromycin can be taken with or without food 7
• For sexually transmitted infections or situations where adherence is uncertain, directly observe the first dose when possible 8

Critical Safety Precautions

• Obtain baseline ECG in patients with cardiac risk factors before initiating therapy, and avoid azithromycin if QTc >450 ms (men) or >470 ms (women) 1
• Do not use azithromycin as monotherapy for gonococcal infections due to widespread resistance; must combine with ceftriaxone 1
• Azithromycin is NOT first-line for streptococcal pharyngitis due to increasing macrolide resistance in group A Streptococcus 1

Common Adverse Effects

• Gastrointestinal symptoms (nausea, vomiting, abdominal pain, diarrhea) occur in approximately 6-10% of patients but are generally mild to moderate 8, 3
• Azithromycin is better tolerated than erythromycin and has fewer gastrointestinal side effects 5, 6

Special Populations

• Azithromycin is Pregnancy Category B and considered safe in pregnancy 8
• It is preferred over erythromycin in infants <1 month due to lower risk of infantile hypertrophic pyloric stenosis 1