Azithromycin Z-Pack Dosing
The standard Z-pack regimen is 500 mg orally on day 1, followed by 250 mg once daily on days 2 through 5, for a total 5-day course. 1
Standard Adult Dosing Regimens
Respiratory Tract Infections
- 500 mg on day 1, then 250 mg daily for days 2-5 (classic Z-pack) for community-acquired pneumonia, acute bacterial sinusitis, and acute exacerbations of chronic bronchitis 1, 2
- This 5-day regimen delivers a total dose of 1.5 grams and maintains therapeutic tissue concentrations for up to 10 days after the last dose due to azithromycin's prolonged tissue half-life 3
Alternative 3-Day Regimen
- 500 mg once daily for 3 consecutive days is equally effective for respiratory infections, also delivering 1.5 grams total 2, 4
- Both the 3-day and 5-day regimens achieve tissue concentrations exceeding MICs for key respiratory pathogens (S. pneumoniae, H. influenzae, S. pyogenes) for approximately 10 days 3
Single-Dose Regimen for STIs
- 1 gram as a single oral dose for chlamydial urethritis and cervicitis 5, 1
- This single dose provides therapeutic urogenital tissue concentrations for approximately 10 days 3, 6
- Patients must abstain from sexual intercourse for 7 days after treatment to prevent transmission 1
Pediatric Dosing
Standard Pediatric Regimens
- 10 mg/kg (maximum 500 mg) on day 1, followed by 5 mg/kg (maximum 250 mg) daily on days 2-5 for most respiratory infections 1
- 10 mg/kg once daily for 3 days is an alternative regimen for otitis media and respiratory infections 7
Streptococcal Pharyngitis (Special Case)
- 12 mg/kg once daily for 5 days (maximum 500 mg/day) is required for streptococcal pharyngitis, as standard dosing results in higher recurrence rates compared to penicillin 8, 7
- Azithromycin is reserved for penicillin-allergic patients in this indication 8
Administration Considerations
Timing and Food
- Can be administered with or without food 8
- Separate from aluminum or magnesium-containing antacids by at least 2 hours, as these reduce absorption by up to 50% 1, 8
Compliance Optimization
- Dispense medication on-site when possible and observe the first dose to maximize adherence 1
- Once-daily dosing significantly improves compliance compared to multiple-daily-dose regimens 2, 6
Common Pitfalls and Caveats
Tolerability
- Gastrointestinal side effects (nausea, vomiting, abdominal pain, diarrhea) occur but are less frequent than with erythromycin 1, 7
- In pediatric studies, only 2% reported adverse effects with azithromycin versus 13% with penicillin V 8
Pregnancy
- Azithromycin is FDA Pregnancy Category B and is safe for use in pregnancy 1
- The 1-gram single dose is an alternative regimen for chlamydial infections in pregnant women 5, 1