How to Order a Z-Pack for Bacterial Infection
For most bacterial infections requiring azithromycin, prescribe the standard 5-day Z-pack regimen: 500 mg on day 1, followed by 250 mg once daily on days 2-5. 1, 2
Standard Adult Dosing by Indication
Respiratory Tract Infections
- Community-acquired pneumonia (mild severity): 500 mg on day 1, then 250 mg daily on days 2-5 2
- Acute bacterial sinusitis: 500 mg once daily for 3 days 2
- Acute exacerbations of COPD: Either 500 mg daily for 3 days OR the standard 5-day regimen (500 mg day 1, then 250 mg days 2-5) 2
- Pharyngitis/tonsillitis (second-line therapy): 500 mg on day 1, then 250 mg daily on days 2-5 2
Sexually Transmitted Infections
- Non-gonococcal urethritis and cervicitis (Chlamydia): Single 1-gram dose 1, 2
- Chancroid (genital ulcer disease): Single 1-gram dose 2
- Gonococcal infections: Single 2-gram dose, though this should NOT be used as monotherapy due to widespread resistance—always combine with ceftriaxone 1, 3
Skin and Soft Tissue Infections
- Uncomplicated skin/skin structure infections: 500 mg on day 1, then 250 mg daily on days 2-5 2
Pediatric Dosing (Age ≥6 months)
Respiratory Infections
- Community-acquired pneumonia: 10 mg/kg on day 1 (max 500 mg), then 5 mg/kg daily on days 2-5 (max 250 mg) 1, 2
- Acute bacterial sinusitis: 10 mg/kg once daily for 3 days 2
- Acute otitis media: Three options available—30 mg/kg as single dose, OR 10 mg/kg daily for 3 days, OR 10 mg/kg day 1 then 5 mg/kg days 2-5 2
Pharyngitis/Tonsillitis
- Streptococcal pharyngitis: 12 mg/kg once daily for 5 days (NOT the standard 10 mg/kg dose, as lower doses result in higher recurrence rates) 1, 2, 4
Critical Administration Considerations
Timing and Food
- Azithromycin tablets can be taken with or without food 2
- Avoid simultaneous administration with aluminum- or magnesium-containing antacids, as this reduces absorption 1, 5
Compliance Strategies
- Dispense medication on-site when possible to maximize adherence, particularly for single-dose regimens 1
- Directly observe the first dose in populations with erratic healthcare-seeking behavior 1
- The primary advantage of azithromycin over alternatives like doxycycline is the short duration and once-daily dosing, which significantly improves adherence 1
Safety Monitoring and Contraindications
Cardiac Risk Assessment
- Obtain baseline ECG before long-term therapy (>3 weeks) to assess QTc interval 1
- Contraindicate if QTc >450 ms (men) or >470 ms (women) 1
- Azithromycin can cause fatal cardiac arrhythmias including torsades de pointes—avoid in patients with known QT prolongation or history of torsades 3
Hepatic and Renal Considerations
- No dosage adjustment needed for renal impairment (GFR ≥10 mL/min), though exercise caution with severe renal impairment (GFR <10 mL/min) 2
- Measure baseline liver function tests for long-term therapy 1
- Prescribe with caution in patients with impaired hepatic function 5
Resistance Patterns
- Consider local macrolide resistance patterns before prescribing—high resistance may favor alternative agents 3
- Azithromycin's long half-life creates a 14-20 day "window" of subinhibitory drug concentrations that may promote resistance development 3
Common Pitfalls to Avoid
When NOT to Use Azithromycin
- Do NOT use as monotherapy for gonorrhea due to widespread resistance 1, 3
- Doxycycline is preferred for chlamydial infections—use azithromycin only if doxycycline fails, is contraindicated, or adherence is a major concern 3
- Beta-lactams remain first-line for hospitalized patients with community-acquired pneumonia 3
- Amoxicillin-clavulanate shows superior efficacy compared to macrolides in head-to-head trials for acute bacterial sinusitis 3
Special Warnings
- Screen for tuberculosis in high-risk populations before initiating therapy for pneumonia, as empiric azithromycin may delay TB diagnosis 3
- Patients treated for STIs should abstain from sexual intercourse for 7 days after completing therapy to prevent transmission 1