Azithromycin Dosage Calculator for Children
Calculate children's azithromycin (Zithromax, Z-Pack) dosage by weight. Supports both the standard 5-day protocol (10 mg/kg day 1, then 5 mg/kg days 2 to 5) and the 3-day protocol (10 mg/kg daily for 3 days). Shows liquid suspension volumes for 100 mg/5 mL and 200 mg/5 mL concentrations. Commonly prescribed for ear infections, strep throat, pneumonia, and sinusitis in children.
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Formula
How it works: Azithromycin uses a loading dose on day 1 (10 mg/kg) followed by lower maintenance doses (5 mg/kg) on days 2 through 5 in the standard protocol. The 3-day protocol uses the higher 10 mg/kg dose for all 3 days. Both deliver the same total drug exposure. Maximum doses are 500 mg on day 1 and 250 mg on days 2-5.
Worked Example
Azithromycin (Zithromax) Dosing Guide for Children
Azithromycin is a macrolide antibiotic commonly used as a second-line treatment for pediatric infections. Its once-daily dosing and short course improve compliance compared to antibiotics requiring multiple daily doses.
- Standard 5-day protocol: 10 mg/kg on day 1 (loading dose), then 5 mg/kg on days 2 through 5. Total course equals 30 mg/kg
- Short 3-day protocol: 10 mg/kg daily for 3 days. Total course equals 30 mg/kg (same total as 5-day)
- Available as oral suspension in 100 mg/5 mL (for smaller children) and 200 mg/5 mL (standard pediatric concentration)
- Best absorbed on an empty stomach (1 hour before or 2 hours after meals), though it can be taken with food if stomach upset occurs
- Commonly prescribed when amoxicillin fails or the child has a penicillin allergy. Not first-line for strep throat (amoxicillin is preferred)
Complete the full antibiotic course even if symptoms improve after 1 to 2 days. Stopping early contributes to antibiotic resistance. Always confirm dosing with the prescribing physician. For educational reference only.
You can also calculate changes using our Amoxicillin Dosage Calculator, Ibuprofen Dosage Calculator for Children, Paediatric Dosage Calculator or Medication Dosage by Weight Calculator.
Azithromycin Pediatric Dosage Chart (5-Day Protocol)
Standard 5-day dosing chart for azithromycin liquid suspension at 200 mg/5 mL concentration. Day 1 uses a loading dose of 10 mg/kg, followed by 5 mg/kg on days 2 through 5.
| Weight (kg) | Weight (lbs) | Day 1 (mg) | Day 1 (mL) | Days 2-5 (mg) | Days 2-5 (mL) | Total Course |
|---|---|---|---|---|---|---|
| 5 kg | 11 lbs | 50 mg | 1.25 mL | 25 mg | 0.6 mL | 150 mg |
| 8 kg | 18 lbs | 80 mg | 2 mL | 40 mg | 1 mL | 240 mg |
| 10 kg | 22 lbs | 100 mg | 2.5 mL | 50 mg | 1.25 mL | 300 mg |
| 12 kg | 26 lbs | 120 mg | 3 mL | 60 mg | 1.5 mL | 360 mg |
| 15 kg | 33 lbs | 150 mg | 3.75 mL | 75 mg | 1.9 mL | 450 mg |
| 20 kg | 44 lbs | 200 mg | 5 mL | 100 mg | 2.5 mL | 600 mg |
| 25 kg | 55 lbs | 250 mg | 6.25 mL | 125 mg | 3.1 mL | 750 mg |
| 30 kg | 66 lbs | 300 mg | 7.5 mL | 150 mg | 3.75 mL | 900 mg |
| 40 kg | 88 lbs | 400 mg | 10 mL | 200 mg | 5 mL | 1,200 mg |
| 50+ kg | 110+ lbs | 500 mg max | 12.5 mL | 250 mg max | 6.25 mL | 1,500 mg |
Note: Volumes shown for 200 mg/5 mL suspension. For 100 mg/5 mL, double the volume. Give once daily, 1 hour before or 2 hours after meals. Complete the full course. Max: 500 mg day 1, 250 mg days 2-5. For educational reference only.
Frequently Asked Questions
What is the azithromycin dose for a child with an ear infection?
The standard 5-day protocol for acute otitis media is 10 mg/kg on day 1, then 5 mg/kg on days 2 through 5.
For a 15 kg child: 150 mg on day 1, then 75 mg daily for 4 days.
Alternatively, the 3-day protocol uses 10 mg/kg daily for 3 days (150 mg/day for a 15 kg child).
How much Zithromax 200mg/5ml for a 20 kg child?
Day 1: 200 mg = 5 mL of suspension.
Days 2 through 5: 100 mg = 2.5 mL each day.
Give 5 mL on the first day, then 2.5 mL once daily for 4 more days.
Total course: 600 mg over 5 days.
Is the 3-day or 5-day azithromycin course better?
Both deliver the same total drug exposure (30 mg/kg). The 5-day course is traditional and most commonly prescribed. The 3-day course may improve compliance because it is shorter. Studies show similar effectiveness for most pediatric infections. Your doctor will choose based on the specific infection and child's tolerance.
Can azithromycin be taken with food?
Azithromycin suspension is best absorbed on an empty stomach: 1 hour before or 2 hours after a meal. However, if your child experiences stomach upset, it can be taken with food without significantly affecting absorption. Azithromycin tablets can be taken with or without food.
What are the side effects of azithromycin in children?
The most common side effects are diarrhea (5 to 8%), nausea, abdominal pain, and vomiting. These are usually mild and resolve after the course is completed. Rare but serious side effects include allergic reactions and QT prolongation (a heart rhythm concern). Report any rash, difficulty breathing, or irregular heartbeat to your doctor immediately.
When is azithromycin used instead of amoxicillin?
Azithromycin is typically used when:
(1) The child has a confirmed penicillin allergy.
(2) Amoxicillin has failed after 48 to 72 hours of treatment.
(3) The child cannot tolerate the taste or frequency of amoxicillin dosing.
For strep throat and most ear infections, amoxicillin remains the first-line choice per AAP guidelines.
Medical Disclaimer
This calculator is provided for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any decisions based on these results. Do not disregard or delay seeking medical advice because of information obtained from this tool.
AI Assistant
Ask about this calculator
I can help you understand the azithromycin dosage calculator for children formula, interpret your results, and answer follow-up questions.
Try asking
Our AI assistant provides general estimates and advice only. Please consult a qualified healthcare professional before making any health-related decisions.
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