Azithromycin Dosage Regimens for Bacterial Infections
The standard dosage regimen for azithromycin for most bacterial infections in adults is 500 mg on day 1 followed by 250 mg daily for days 2-5, or alternatively 500 mg daily for 3 days depending on the specific infection. 1, 2
Adult Dosing Regimens by Infection Type
Respiratory Tract Infections
- For community-acquired pneumonia (mild severity): 500 mg as a single dose on day 1, followed by 250 mg once daily on days 2-5 2
- For acute bacterial exacerbations of chronic obstructive pulmonary disease: Either 500 mg daily for 3 days OR 500 mg on day 1, followed by 250 mg daily on days 2-5 2
- For acute bacterial sinusitis: 500 mg daily for 3 days 2
- For pharyngitis/tonsillitis (as second-line therapy): 500 mg on day 1, followed by 250 mg once daily on days 2-5 2
Skin and Soft Tissue Infections
- For uncomplicated skin/skin structure infections: 500 mg as a single dose on day 1, followed by 250 mg once daily on days 2-5 2
- For cat scratch disease: 500 mg on day 1 followed by 250 mg for 4 additional days 3
Sexually Transmitted Infections
- For non-gonococcal urethritis and cervicitis: One single 1 gram dose 2
- For genital ulcer disease (chancroid): One single 1 gram dose 2
- For gonococcal urethritis and cervicitis: One single 2 gram dose 2
Pediatric Dosing Regimens
Respiratory Tract Infections
- For acute otitis media:
- 30 mg/kg as a single dose, OR
- 10 mg/kg once daily for 3 days, OR
- 10 mg/kg on day 1 followed by 5 mg/kg/day on days 2-5 2
- For acute bacterial sinusitis: 10 mg/kg once daily for 3 days 2
- For community-acquired pneumonia: 10 mg/kg on day 1 followed by 5 mg/kg on days 2-5 2
- For pharyngitis/tonsillitis: 12 mg/kg once daily for 5 days 2
Other Pediatric Indications
- For pertussis treatment and prophylaxis in infants <6 months: 10 mg/kg per day for 5 days 3
- For pertussis in infants and children >6 months: 10 mg/kg (maximum: 500 mg) on day 1, followed by 5 mg/kg per day (maximum: 250 mg) on days 2-5 3
- For cat scratch disease in patients <45 kg: 10 mg/kg on day 1 and 5 mg/kg for 4 more days 3
Administration Considerations
- Azithromycin tablets can be taken with or without food 2
- If taken with aluminum or magnesium-containing antacids, absorption may be reduced 3
- For patients with renal impairment (GFR ≤80 mL/min), no dosage adjustment is recommended 2
- Caution should be exercised when azithromycin is administered to subjects with severe renal impairment (GFR <10 mL/min) 2
Pharmacokinetic Considerations
- Azithromycin has unique pharmacokinetics characterized by high, sustained tissue concentrations 4
- Tissue concentrations exceed serum concentrations significantly, allowing for shorter treatment regimens 5
- The drug has a long terminal half-life (2-4 days in tissues), enabling once-daily dosing 6, 5
- Concentrations in respiratory tract tissues remain above MICs for key pathogens for up to 10 days after a 3-5 day regimen 4
Clinical Pearls and Cautions
- Before initiating therapy in patients with cardiac risk factors, an ECG should be performed to assess the QTc interval 1
- Azithromycin should be avoided if the QTc interval is >450 ms for men and >470 ms for women 1
- Single-dose regimens for certain infections improve compliance through directly observed therapy 3
- Common side effects include abdominal discomfort/pain, diarrhea, nausea, vomiting, headache, and dizziness 3
- The short-duration, once-daily dosing regimen is generally well tolerated in both adults and children 6
- For Lyme disease, azithromycin is considered an alternative agent when first-line treatments cannot be used 7
Antimicrobial Stewardship Considerations
- Limit antibiotic exposure whenever possible to minimize development of resistance 1
- Consider viral etiology of many respiratory infections before prescribing antibiotics 1
- Treatment with the shortest effective duration minimizes exposure of both pathogens and normal microbiota to antimicrobials 1
- Assessment of response to therapy at days 5-7 is recommended 1