Azithromycin Dosing and Safety Guidelines

Standard Adult Regimen

• The recommended adult “Z‑Pack” consists of 500 mg on day 1 followed by 250 mg once daily on days 2‑5 (total 1.5 g), approved for common respiratory and soft‑tissue infections. 1

Pediatric Regimens

• For children > 6 months, give 10 mg/kg (max 500 mg) as a single dose on day 1, then 5 mg/kg (max 250 mg) daily on days 2‑5. 2
• Infants < 6 months receive 10 mg/kg each day for 5 days. 1

Indication‑Specific Dosing

Chlamydial Infections

• A single 1‑g oral dose is recommended for adults and for children ≥ 8 years or weighing > 45 kg. [3][4]

Lyme Disease (when β‑lactams or doxycycline are contraindicated)

• Adults: 500 mg orally once daily for 7‑10 days.
• Children: 10 mg/kg (max 500 mg) once daily for 7‑10 days.
• Macrolides are not first‑line; they should be used only with close monitoring when other agents cannot be used. [5][6]

Babesiosis (combined with atovaquone)

• Adults: 500‑1000 mg on day 1, then 250 mg daily for 7‑10 days.
• Immunocompromised adults may require 600‑1000 mg daily.
• Children: 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg daily for 7‑10 days. [2][7]

Pertussis

• Infants < 6 months: 10 mg/kg daily for 5 days.
• Infants ≥ 6 months and children: 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg (max 250 mg) on days 2‑5.
• Adults: 500 mg day 1, then 250 mg daily days 2‑5. 1

Long‑Term Prophylactic Use (Chronic Respiratory Conditions)

• Options: 250 mg three times weekly, or 500 mg three times weekly, or 250 mg daily.
• Therapy should continue for a minimum of 6‑12 months to evaluate efficacy.
• Baseline ECG is required; therapy is contraindicated if QTc > 450 ms (men) or > 470 ms (women). 8

Safety Considerations

Contraindications & Precautions

• Known macrolide hypersensitivity or prolonged QTc interval. [1][8]
• Pregnancy: FDA Category B (generally considered safe). 1
• Infants < 1 month have an increased risk of infantile hypertrophic pyloric stenosis; azithromycin is preferred over erythromycin but monitoring is advised. [1][4]

Drug‑Interaction Alerts

• Avoid concurrent aluminum or magnesium antacids.
• Use caution with drugs metabolized by CYP 450 enzymes, digoxin, triazolam, and ergot alkaloids. 1

Clinical Use Caveats

• Azithromycin should not be used as monotherapy for gonococcal infections because of resistance concerns. [3][4]
• For severe infections requiring hospitalization, parenteral antimicrobial therapy is generally preferred over oral macrolides. 9