What is the recommended dose for azithromycin?

Azithromycin Dosing

For most adult infections, azithromycin is dosed as 500 mg on day 1 followed by 250 mg daily on days 2-5, but for sexually transmitted infections like chlamydia, a single 1 gram dose is preferred. 1

Adult Dosing by Indication

Sexually Transmitted Infections

• Non-gonococcal urethritis and cervicitis (chlamydia): Single 1 gram oral dose 1, 2
• Gonococcal urethritis and cervicitis: Single 2 gram oral dose 1
• Chancroid (genital ulcer disease): Single 1 gram oral dose 1
• Patients must abstain from sexual intercourse for 7 days after single-dose therapy to prevent transmission 2

Respiratory Tract Infections

• Community-acquired pneumonia (mild): 500 mg on day 1, then 250 mg once daily on days 2-5 1
• Acute bacterial exacerbations of COPD: Either 500 mg daily for 3 days OR 500 mg on day 1, then 250 mg daily on days 2-5 1
• Acute bacterial sinusitis: 500 mg daily for 3 days 1
• Pharyngitis/tonsillitis (second-line): 500 mg on day 1, then 250 mg daily on days 2-5 1

Skin and Soft Tissue Infections

• Uncomplicated skin/skin structure infections: 500 mg on day 1, then 250 mg daily on days 2-5 1

Specialized Indications

• Cat scratch disease (>45 kg): 500 mg on day 1, then 250 mg daily for 4 additional days 2
• Babesiosis (with atovaquone): 500-1000 mg on day 1, then 250 mg daily thereafter 2
• Disseminated MAC disease in AIDS: 250 mg daily with ethambutol 2
• MAC prophylaxis in AIDS (CD4 <50): 1200 mg once weekly 2

Pediatric Dosing (≥6 months)

Respiratory Infections

• Acute otitis media: Three options available 1
  • Single 30 mg/kg dose (maximum 1500 mg)
  • 10 mg/kg daily for 3 days
  • 10 mg/kg on day 1, then 5 mg/kg daily on days 2-5
• Community-acquired pneumonia: 10 mg/kg on day 1, then 5 mg/kg daily on days 2-5 1
• Acute bacterial sinusitis: 10 mg/kg daily for 3 days 1
• Pharyngitis/tonsillitis (≥2 years): 12 mg/kg daily for 5 days 1, 3

Special Pediatric Populations

• Pertussis (<6 months): 10 mg/kg daily for 5 days 2
• Pertussis (≥6 months): 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg daily (max 250 mg) on days 2-5 2
• Chlamydial conjunctivitis in neonates: 20 mg/kg daily for 3 days 2
• Cat scratch disease (<45 kg): 10 mg/kg on day 1, then 5 mg/kg daily for 4 days 2

Administration Considerations

• Can be taken with or without food for both tablets and oral suspension 1
• Avoid aluminum or magnesium-containing antacids as they reduce absorption 2
• Directly observed first dose is recommended for STI treatment to maximize compliance 2
• Dispense medication on-site when possible to improve adherence 2

Special Populations

Pregnancy

• Azithromycin 1 gram single dose is safe and recommended for chlamydial infections in pregnancy 4, 2
• Azithromycin is FDA Pregnancy Category B 2
• Doxycycline is contraindicated in pregnancy 4

Renal Impairment

• No dose adjustment needed for GFR 10-80 mL/min 1
• Use caution in severe renal impairment (GFR <10 mL/min) as AUC increases 35% 1

Hepatic Impairment

• No specific dosing recommendations available due to lack of pharmacokinetic data 1

Infants <1 Month

• Azithromycin is preferred over erythromycin due to lower risk of infantile hypertrophic pyloric stenosis 2

Common Pitfalls

• For pharyngitis/tonsillitis, the standard 5-day regimen may result in more recurrences than penicillin, necessitating the higher 12 mg/kg daily dose in children 3
• Gastrointestinal side effects (abdominal pain, diarrhea, nausea, vomiting) are common but less frequent than with erythromycin 2, 1
• The single-dose advantage for STIs is improved compliance and allows for directly observed therapy 2
• Tissue half-life is prolonged, providing therapeutic concentrations for approximately 10 days after a single 1 gram dose 2