100 mg per 5 mL (20 mg/mL)
200 mg per 5 mL (40 mg/mL)
Standard 5-Day (10mg/kg Day 1, then 5mg/kg)
Pharyngitis/Tonsillitis (12mg/kg for 5 days)
3-Day Course (10mg/kg daily)
Recommended Dosage Schedule
Day
Dose (mg)
Volume (mL)
Important: This calculator is for educational purposes only. Always verify the dose with a qualified healthcare professional or pharmacist before administering medication to a child. Never exceed adult maximum doses (usually 500mg/day).
Understanding Azithromycin Dosing for Children
Azithromycin (commonly known by the brand name Zithromax) is a macrolide antibiotic frequently prescribed to children for bacterial infections such as middle ear infections (otitis media), pneumonia, and strep throat. Unlike many other antibiotics, azithromycin has a long half-life, allowing for shorter treatment courses.
How the Calculation Works
Pediatric medication is almost always weight-based to ensure efficacy and safety. The two primary factors needed for an accurate calculation are:
The Child's Weight: Measured in kilograms (kg). If you weigh your child in pounds, divide the weight by 2.2046 to get kilograms.
The Clinical Indication: Different infections require different "mg/kg" ratios. For example, Strep throat typically requires a higher daily dose (12mg/kg) than a standard ear infection (10mg/kg on Day 1).
Common Dosage Regimens
Most azithromycin prescriptions for children follow one of three patterns:
The 5-Day "Z-Pak" Style: 10 mg/kg of body weight on the first day, followed by 5 mg/kg for the remaining four days.
The 3-Day Course: 10 mg/kg given once daily for three consecutive days.
Pharyngitis/Tonsillitis: Specifically for Strep throat, the dose is often 12 mg/kg daily for five days.
Liquid Concentrations Explained
Azithromycin oral suspension usually comes in two strengths. It is vital to check the bottle for the concentration:
100 mg / 5 mL: This means every 1 mL of liquid contains 20 mg of medicine.
200 mg / 5 mL: This means every 1 mL of liquid contains 40 mg of medicine.
Safety Reminders
Always use the specific oral syringe or measuring cup provided with the medication. Kitchen teaspoons are not accurate for measuring medicine. If your child vomits within 30 minutes of taking the dose, contact your pediatrician to ask if the dose should be repeated.
function calculateAzithroDose() {
var weightInput = document.getElementById('childWeight').value;
var unit = document.getElementById('weightUnit').value;
var concentration = parseFloat(document.getElementById('concentration').value);
var regimen = document.getElementById('regimen').value;
var resultDiv = document.getElementById('azithro-results');
var tableBody = document.getElementById('dosageTableBody');
var weightDisplay = document.getElementById('weightDisplay');
if (!weightInput || weightInput <= 0) {
alert("Please enter a valid weight.");
return;
}
var weightKg = parseFloat(weightInput);
if (unit === 'lb') {
weightKg = weightKg * 0.453592;
}
weightDisplay.innerText = "Calculated for Weight: " + weightKg.toFixed(2) + " kg (" + (weightKg * 2.20462).toFixed(1) + " lbs)";
tableBody.innerHTML = "";
var schedule = [];
if (regimen === 'standard') {
// Day 1: 10mg/kg, Days 2-5: 5mg/kg
schedule.push({ day: "Day 1", mg: weightKg * 10 });
for (var i = 2; i <= 5; i++) {
schedule.push({ day: "Day " + i, mg: weightKg * 5 });
}
} else if (regimen === 'pharyngitis') {
// 12mg/kg for 5 days
for (var i = 1; i <= 5; i++) {
schedule.push({ day: "Day " + i, mg: weightKg * 12 });
}
} else if (regimen === 'threeday') {
// 10mg/kg for 3 days
for (var i = 1; i <= 3; i++) {
schedule.push({ day: "Day " + i, mg: weightKg * 10 });
}
}
for (var j = 0; j 500) mgDose = 500;
else if (regimen === 'standard' && j === 0 && mgDose > 500) mgDose = 500;
else if (regimen === 'standard' && j > 0 && mgDose > 250) mgDose = 250;
else if (regimen === 'threeday' && mgDose > 500) mgDose = 500;
var mlDose = mgDose / concentration;
var row = tableBody.insertRow();
var cell1 = row.insertCell(0);
var cell2 = row.insertCell(1);
var cell3 = row.insertCell(2);
cell1.innerHTML = "" + schedule[j].day + "";
cell2.innerText = mgDose.toFixed(1) + " mg";
cell3.innerHTML = "" + mlDose.toFixed(2) + " mL";
}
resultDiv.style.display = "block";
resultDiv.scrollIntoView({ behavior: 'smooth' });
}