Actemra (tocilizumab) is a valuable biologic medication used to treat various autoimmune and inflammatory conditions, including Rheumatoid Arthritis (RA), Polyarticular Juvenile Idiopathic Arthritis (pJIA), Systemic Juvenile Idiopathic Arthritis (sJIA), Giant Cell Arteritis (GCA), and Ulcerative Colitis (UC).
Accurate dosing is critical for efficacy and patient safety. Dosing for Actemra is typically based on the patient's weight, the specific indication being treated, and the chosen administration frequency (subcutaneous injection). This calculator helps healthcare professionals determine the appropriate dose.
How the Calculation Works:
The calculation involves a simple multiplication of the patient's weight in kilograms by the recommended dose per kilogram (mg/kg) for the selected indication.
Patient Weight: The starting point is the patient's weight in kilograms (kg).
Indication-Specific Dose: Each indication has a standard dose range or fixed dose administered per kilogram of body weight. For example:
Rheumatoid Arthritis (RA), Giant Cell Arteritis (GCA), and Uveitis (UI): Typically 162 mg (given subcutaneously) once weekly or every two weeks. The calculator focuses on the total milligram dose per administration based on weight for RA, GCA, and UI, assuming 162 mg per injection at specific frequencies. For RA, GCA, and UI, the calculation primarily determines the frequency and confirms the 162mg injection.
Polyarticular Juvenile Idiopathic Arthritis (pJIA): May be dosed at 10 mg/kg or 8 mg/kg, depending on the situation and healthcare provider's discretion.
Systemic Juvenile Idiopathic Arthritis (sJIA): Typically 12 mg/kg for patients under 30 kg and 8 mg/kg for patients 30 kg or greater, given every two weeks. For simplicity, the calculator may present a fixed dose or a weight-based calculation for the higher end if a specific weight threshold isn't critical for the calculator's primary function (e.g., presenting the typical mg/kg).
Ulcerative Colitis (UC): Typically 150 mg given every four weeks (monthly). The calculator's output for UC is primarily the confirmation of this fixed dose and frequency.
Dosing Frequency: The frequency (weekly, bi-weekly, monthly) dictates how often the calculated dose is administered.
Formula (for weight-based indications): Dose (mg) = Patient Weight (kg) × Dose per kg (mg/kg)
Example:
For Rheumatoid Arthritis (RA) at 162 mg per dose, a patient weighing 75 kg would receive 162 mg subcutaneously once weekly or every two weeks, as determined by their physician.
For Polyarticular JIA using the 10 mg/kg option, a patient weighing 25 kg would receive 25 kg * 10 mg/kg = 250 mg.
For Systemic JIA, a patient weighing 35 kg might receive 12 mg/kg * 35 kg = 420 mg every two weeks (or 8 mg/kg * 35 kg = 280 mg based on weight threshold). The calculator simplifies this to the mg/kg value.
For Ulcerative Colitis, a patient would receive 150 mg once monthly, regardless of weight within the standard treatment guidelines.
Disclaimer: This calculator is for informational purposes only and does not substitute professional medical advice. Always consult with a qualified healthcare provider for diagnosis and treatment decisions regarding Actemra. Dosing should be individualized based on patient factors and clinical judgment.
function calculateDose() {
var weight = parseFloat(document.getElementById("patientWeight").value);
var indicationSelect = document.getElementById("indication");
var selectedIndicationValue = indicationSelect.value;
var selectedOption = indicationSelect.options[indicationSelect.selectedIndex];
var dosePerKg = parseFloat(selectedOption.getAttribute("data-dose-mg-kg"));
var frequency = document.getElementById("frequency").value;
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = "; // Clear previous results
if (isNaN(weight) || weight <= 0) {
resultDiv.innerHTML = "Please enter a valid patient weight.";
return;
}
var calculatedDoseMg;
var displayFrequency = "";
var specificNotes = "";
if (selectedIndicationValue === "RA" || selectedIndicationValue === "GCA" || selectedIndicationValue === "𝙪IG") {
// For RA, GCA, UI, the primary dose is 162mg, frequency is what matters.
calculatedDoseMg = 162; // Standard SC dose
if (frequency === "weekly") {
displayFrequency = "Once Weekly";
} else if (frequency === "bi-weekly") {
displayFrequency = "Every Two Weeks";
} else {
displayFrequency = "Every Two Weeks"; // Default if monthly selected but not typical for RA SC
specificNotes += "Note: Monthly dosing is not standard for SC Actemra in these indications. Confirm with prescriber.";
}
specificNotes += "This dose (162mg) is typically administered regardless of weight in this range for these indications.";
} else if (selectedIndicationValue === "colitis") {
// For UC, the dose is fixed at 150mg, frequency is monthly.
calculatedDoseMg = 150; // Standard UC dose
displayFrequency = "Once Monthly (Every Four Weeks)";
specificNotes += "This dose (150mg) is typically administered regardless of weight for Ulcerative Colitis.";
} else if (selectedIndicationValue === "JIA") {
// pJIA 10 mg/kg
calculatedDoseMg = weight * dosePerKg;
displayFrequency = "Every " + (frequency === "weekly" ? "Week" : (frequency === "bi-weekly" ? "Two Weeks" : "Week")); // Frequency often every two weeks for JIA
if(frequency === "monthly") {
displayFrequency = "Monthly";
specificNotes += "Note: Monthly dosing for pJIA may not be standard. Confirm with prescriber.";
}
// Round to nearest whole number for practical dosing
calculatedDoseMg = Math.round(calculatedDoseMg);
} else if (selectedIndicationValue === "JIA_8") {
// pJIA 8 mg/kg
calculatedDoseMg = weight * dosePerKg;
displayFrequency = "Every " + (frequency === "weekly" ? "Week" : (frequency === "bi-weekly" ? "Two Weeks" : "Week")); // Frequency often every two weeks for JIA
if(frequency === "monthly") {
displayFrequency = "Monthly";
specificNotes += "Note: Monthly dosing for pJIA may not be standard. Confirm with prescriber.";
}
// Round to nearest whole number for practical dosing
calculatedDoseMg = Math.round(calculatedDoseMg);
} else if (selectedIndicationValue === "sJIA") {
// sJIA: 12 mg/kg for = 30kg. Calculator uses the selected dosePerKg (12mg/kg in this case as default for dropdown)
// For a simplified calculator, we can present based on the selected option's mg/kg.
// A more complex calculator would branch based on weight threshold for sJIA.
calculatedDoseMg = weight * dosePerKg;
displayFrequency = "Every " + (frequency === "bi-weekly" ? "Two Weeks" : "Week"); // Often every two weeks
if(frequency === "weekly" || frequency === "monthly") {
displayFrequency = frequency === "weekly" ? "Once Weekly" : "Once Monthly";
specificNotes += "Note: Weekly or Monthly dosing for sJIA may not be standard. Confirm with prescriber.";
}
// Round to nearest whole number for practical dosing
calculatedDoseMg = Math.round(calculatedDoseMg);
specificNotes += "Note: For sJIA, dosing may differ based on weight thresholds (e.g., 12 mg/kg for =30kg). Consult guidelines or prescriber.";
} else {
resultDiv.innerHTML = "Invalid indication selected.";
return;
}
// Ensure the calculated dose is not excessively high and provide feedback
var maxDoseMg = 162; // Common upper limit for SC injections
if (selectedIndicationValue === "colitis") maxDoseMg = 150; // UC max dose
if (selectedIndicationValue === "JIA" || selectedIndicationValue === "JIA_8" || selectedIndicationValue === "sJIA") {
// These are weight-based, so max dose can be higher, but let's set a sensible upper bound for typical scenarios.
// A more robust calculator would handle specific drug product maximums.
// For these, we'll just ensure the calculation is displayed.
}
var finalDoseOutput;
if (selectedIndicationValue === "RA" || selectedIndicationValue === "GCA" || selectedIndicationValue === "colitis" || selectedIndicationValue === "𝙪IG") {
finalDoseOutput = `${calculatedDoseMg} mg ${displayFrequency}`;
} else {
// For weight-based JIA indications
finalDoseOutput = `${calculatedDoseMg} mg (${weight} kg × ${dosePerKg} mg/kg) ${displayFrequency}`;
}
resultDiv.innerHTML = `Your recommended dose is: ${finalDoseOutput}${specificNotes}`;
}