Azithromycin Pediatric Dose Calculator
Calculate azithromycin (Zithromax) doses for children by weight for otitis media, pharyngitis, pneumonia, and sinusitis with day-by-day dosing.
Azithromycin Pediatric Dose Calculator
Evidence-based weight-adjusted dosing
How to Use This Calculator
Enter Weight
Input the child's current weight in kilograms.
Select Indication
Choose the infection type — each has a unique dosing schedule.
Choose Formulation
Select the suspension concentration or tablet form.
Review Day-by-Day Dosing
See the Day 1 dose and subsequent daily doses with volumes in mL.
How We Calculate
Azithromycin dosing in pediatrics follows a distinctive loading-dose pattern for most indications. For acute otitis media and community-acquired pneumonia, the AAP and IDSA recommend 10 mg/kg on Day 1 (max 500 mg) followed by 5 mg/kg (max 250 mg) on Days 2–5, given once daily. For pharyngitis, 12 mg/kg/day (max 500 mg) for 5 days is the standard regimen.
Azithromycin's prolonged tissue half-life of 68 hours means therapeutic levels persist for several days after the last dose, effectively providing 10 days of antimicrobial coverage from a 5-day course. The two available suspension concentrations (100 mg/5 mL and 200 mg/5 mL) accommodate different age groups and weight ranges.
Azithromycin should be used judiciously due to rising macrolide resistance among S. pneumoniae and Group A Streptococcus. It is not a first-line agent for pharyngitis or otitis media but serves as an important alternative for penicillin-allergic patients. This calculator is for educational reference only.
Sources & References
- AAP Red Book — Report of the Committee on Infectious Diseases (aap.org)
- IDSA/ATS Guidelines for Community-Acquired Pneumonia in Children (idsociety.org)
- Lexicomp Pediatric Drug Information — Azithromycin (wolterskluwer.com)
Data last verified:
Frequently Asked Questions
A Z-Pack (Zithromax Z-Pak) is a pre-packaged adult dosing regimen containing six 250 mg tablets: 500 mg on Day 1 and 250 mg on Days 2-5. Pediatric dosing is weight-based and uses liquid suspension for accurate dosing in younger children. Children should NOT use adult Z-Packs unless they are large enough that the weight-based dose matches the adult dose and can swallow tablets.
Azithromycin suspension can be taken with or without food. However, the tablet form has better absorption when taken on an empty stomach (1 hour before or 2 hours after meals). The suspension is not affected by food and can be given with meals to improve palatability and reduce stomach upset in children who are sensitive.
Azithromycin has an exceptionally long tissue half-life of approximately 68 hours, which allows once-daily dosing. The drug concentrates in tissues at levels 10-100 times higher than plasma levels and is slowly released over days. This pharmacokinetic property also explains why a 5-day course provides antimicrobial coverage equivalent to 10 days of other antibiotics.
Azithromycin carries a small risk of QT interval prolongation, which can theoretically lead to abnormal heart rhythms. The risk is highest in patients with pre-existing QT prolongation, electrolyte abnormalities, or those taking other QT-prolonging medications. In otherwise healthy children, this risk is very low. The prescriber should be informed of any known cardiac conditions or family history of long QT syndrome.
Reconstituted azithromycin suspension should be stored at room temperature (5-30°C / 41-86°F). Unlike many other antibiotic suspensions, it does NOT require refrigeration, though refrigeration is acceptable and may improve taste. The reconstituted suspension is stable for 10 days and should be discarded after that. Shake well before each dose and use the provided measuring device.
If a dose is missed, give it as soon as remembered. If it is almost time for the next dose, skip the missed dose and continue the regular schedule. Do not double up doses. For the loading-dose regimen (10/5), if Day 1 is missed, give the loading dose when remembered and continue the 5-day count from that point. Contact the prescriber if multiple doses are missed.
Yes, the full prescribed course should be completed even if the child feels better before finishing the medication. Stopping early can lead to incomplete bacterial eradication, which promotes antibiotic resistance. For a 5-day azithromycin course, the extended tissue half-life means stopping even one day early significantly reduces the total antimicrobial exposure.
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