About this Calculator

The Kadcyla (ado-trastuzumab emtansine) Dosing Calculator is a clinical support tool designed to help healthcare professionals determine the appropriate dose and vial combination based on patient weight and the recommended dosing schedule. It automates calculations according to the official prescribing information, including dose reductions for toxicity management.

Outputs

After entering the required patient data, the calculator provides the following key outputs:

• Total Milligram (mg) Dose: The precise dose calculated from the patient's weight in kilograms and the selected mg/kg dose level.
• Recommended Vial Combination: The most efficient combination of 100 mg and 160 mg vials needed to prepare the dose, calculated to minimize drug waste.
• Total Drug in Vials: The total amount of medication available from the recommended vial combination.
• Dose Modification Guidance: Based on selected laboratory values (e.g., platelets, LVEF, liver function tests), the tool provides recommendations to hold, reduce, or continue treatment, aligning with safety guidelines.

How to Use

Follow these simple steps to calculate the correct dose:

1. Enter Patient Weight: Input the patient's current weight into the designated field.
2. Select Weight Unit: Choose between kilograms (kg) or pounds (lbs). The tool will automatically convert lbs to kg for the calculation (1 kg = 2.20462 lbs).
3. Select Dose Level: From the dropdown menu, choose the appropriate dose (3.6 mg/kg for starting dose, or reduced levels of 3.0 mg/kg or 2.4 mg/kg).
4. Check for Toxicities (Optional): Use the Dose Modification Guidance section to select any relevant laboratory abnormalities. The tool will display the recommended action based on these inputs.

Dosing Overview

Kadcyla is administered as an intravenous infusion every 3 weeks (21-day cycle). The standard recommended dose is 3.6 mg/kg. It should not be administered as an IV push or bolus. The initial infusion should be given over 90 minutes; subsequent infusions may be administered over 30 minutes if the first is well tolerated. Patients should be monitored for infusion-related reactions.

Dose Modifications

Dose reductions may be required to manage treatment-related toxicities. The standard dose reduction schedule is as follows:

• Starting Dose: 3.6 mg/kg
• First Dose Reduction: 3.0 mg/kg
• Second Dose Reduction: 2.4 mg/kg

Treatment with Kadcyla should be permanently discontinued if a patient requires a dose reduction below 2.4 mg/kg.

Missed Dose

If a scheduled dose of Kadcyla is missed, it should be administered as soon as possible. The administration schedule should then be adjusted to maintain a 3-week interval between doses. Do not wait until the next planned cycle to give the missed dose.

Safety Alerts

Kadcyla has Boxed Warnings for hepatotoxicity, cardiotoxicity, and embryo-fetal toxicity. Before each dose, clinicians must monitor liver function tests (transaminases and bilirubin) and left ventricular ejection fraction (LVEF). Treatment may need to be interrupted, dose-reduced, or permanently discontinued based on the severity of these adverse reactions.

References

• KADCYLA® (ado-trastuzumab emtansine) Prescribing Information. Genentech, Inc.
• Kadcyla for Healthcare Professionals. Genentech, Inc.
• FDA Drug Approval Package: KADCYLA (ado-trastuzumab emtansine). U.S. Food and Drug Administration.
• Ado-Trastuzumab Emtansine. National Cancer Institute.