About This Calculator

The Ocrevus (ocrelizumab) Dosing Calculator is designed to assist healthcare professionals in determining the appropriate dosing schedule and infusion rates based on the official prescribing information. This tool simplifies the process of planning the initial and subsequent doses, including calculating key dates and providing standardized infusion rate tables for administration.

It is intended for educational purposes and should always be used in conjunction with clinical judgment and the full prescribing information.

Calculator Outputs

Based on the selected regimen and date, the calculator provides the following key information:

• Dose & Volume: Specifies the total dose (300 mg or 600 mg) and the corresponding volume of ocrelizumab (10 mL or 20 mL) to be withdrawn from the vial(s). Ocrelizumab is supplied in 300 mg/10 mL single-dose vials.
• Next Infusion Date: Calculates the date for the second part of the initial dose (14 days after the first) or the next 6-month subsequent dose.
• Infusion Rate Tables: Displays detailed, step-by-step titration schedules for infusion administration. For subsequent doses, it provides tables for both the standard 3.5-hour infusion and the shorter 2-hour infusion option for eligible patients.

How to Use the Calculator

To use the tool effectively, follow these steps:

1. Select Dosing Regimen: Choose “Initial Dose” for patients starting treatment or “Subsequent Dose” for patients receiving their maintenance infusions.
2. Enter the Relevant Date:
   • For the Initial Dose, enter the date of the very first 300 mg infusion.
   • For a Subsequent Dose, enter the date of the last 600 mg infusion.
3. Enter Patient Weight (Optional): Patient weight is not used to calculate the ocrelizumab dose but may be entered for record-keeping. The tool will not change the dose based on weight.
4. Calculate: Click the “Calculate Dose” button to generate the complete dosing and infusion schedule.

Dosing Overview

Ocrevus administration follows a two-phase schedule: an initial (induction) dose and subsequent (maintenance) doses.

• Initial Dose: The starting dose is 600 mg administered as two separate intravenous infusions. The first is a 300 mg infusion, followed two weeks later by a second 300 mg infusion.
• Subsequent Doses: Following the initial dose, patients receive a single 600 mg intravenous infusion every 6 months.

Pre-medication with a corticosteroid (e.g., methylprednisolone), an antihistamine, and an antipyretic is recommended approximately 30-60 minutes prior to every infusion to reduce the risk of infusion-related reactions.

Switching and Missed Doses

Safety Alerts

Ocrevus has important warnings and precautions that must be considered before and during treatment. The following is not an exhaustive list:

• Infusion-Related Reactions (IRRs): IRRs are common and can be serious. Patients must be monitored during and for at least one hour after infusion. Pre-medication is recommended to mitigate risk.
• Infections: Treatment may increase the risk of infections. Screen for Hepatitis B virus (HBV) prior to initiation, as reactivation can occur. Do not administer during an active infection.
• Progressive Multifocal Leukoencephalopathy (PML): Although rare, cases of PML have been reported. It is a serious brain infection that can lead to severe disability or death.
• Malignancies: An increased risk of malignancies, including breast cancer, has been observed in clinical trials.

Frequently Asked Questions

1. Why is the initial Ocrevus dose split into two infusions?
   The split initial dose is designed to improve the tolerability of the medication and reduce the incidence and severity of infusion-related reactions as the body first gets accustomed to the drug.
2. Does patient weight affect the ocrelizumab dose?
   No. The dose of Ocrevus is fixed at 300 mg for the initial split infusions and 600 mg for subsequent infusions, regardless of the patient’s body weight.
3. Who is eligible for the shorter 2-hour subsequent infusion?
   Patients who have not experienced a serious infusion reaction with any previous Ocrevus infusion are eligible. It is not for use as the initial dose.
4. What premedications are required before an infusion?
   The recommended premedication regimen includes 100 mg of methylprednisolone (or an equivalent corticosteroid), an antihistamine (like diphenhydramine), and an antipyretic (like acetaminophen), administered 30-60 minutes before the infusion.
5. Why is Hepatitis B virus (HBV) screening necessary?
   Ocrevus can cause HBV reactivation, which may lead to fulminant hepatitis, hepatic failure, and death. All patients must be screened for HBsAg and anti-HBc before starting treatment.
6. What should be done if an infusion reaction occurs?
   The infusion rate should be slowed or the infusion interrupted, depending on the severity of the reaction. Symptomatic treatment should be provided. The infusion may be resumed at a lower rate once symptoms resolve.
7. How is Ocrevus supplied?
   Ocrevus is supplied as a concentrate in single-dose vials containing 300 mg of ocrelizumab in 10 mL of solution.
8. What is the final volume of the diluted infusion bag?
   The required dose (10 mL for 300 mg or 20 mL for 600 mg) is withdrawn from the vial(s) and diluted into a 250 mL or 500 mL infusion bag of 0.9% Sodium Chloride Injection. The total volume will depend on the bag size used.

References

1. OCREVUS (ocrelizumab) injection, for intravenous use. U.S. Prescribing Information. Genentech, Inc.
2. Dosing and Administration | OCREVUS® (ocrelizumab) HCP. Genentech, Inc.
3. Ocrevus (ocrelizumab) Summary of Product Characteristics. European Medicines Agency.
4. Ocrevus (ocrelizumab). National Multiple Sclerosis Society.