Zevalin Dosage

Recommended Dosing Schedule

• Administer the Zevalin therapeutic regimen as outlined below.
• Initiate the Zevalin therapeutic regimen following recovery of platelet counts to 150,000/mm3 or more at least 6 weeks, but no more than 12 weeks, following the last dose of first-line chemotherapy.
• Only administer rituximab/Zevalin in facilities where immediate access to resuscitative measures is available.

Overview of Dosing Schedule

Zevalin Therapeutic Regimen Dosage and Administration

Day 1:

• Premedicate with acetaminophen 650 mg orally and diphenhydramine 50 mg orally prior to rituximab infusion.
• Administer rituximab 250 mg/m2 intravenously at an initial rate of 50 mg/hr. In the absence of infusion reactions, escalate the infusion rate in 50 mg/hr increments every 30 minutes to a maximum of 400 mg/hr. Do not mix or dilute rituximab with other drugs.
• Immediately stop the rituximab infusion for serious infusion reactions and discontinue the Zevalin therapeutic regimen [see Boxed Warning and Warnings and Precautions (5.1)].
• Temporarily slow or interrupt the rituximab infusion for less severe infusion reactions. If symptoms improve, continue the infusion at one-half the previous rate.

Day 7, 8 or 9:

• Premedicate with acetaminophen 650 mg orally and diphenhydramine 50 mg orally prior to rituximab infusion.
• Administer rituximab 250 mg/m2 intravenously at an initial rate of 100 mg/hr. Increase rate by 100 mg/hr increments at 30 minute intervals, to a maximum of 400 mg/hr, as tolerated. If infusion reactions occurred during rituximab infusion on Day 1 of treatment, administer rituximab at an initial rate of 50 mg/hr and escalate the infusion rate in 50 mg/hr increments every 30 minutes to a maximum of 400 mg/hr.
• Administer Y-90 Zevalin injection through a free flowing intravenous line within 4 hours following completion of rituximab infusion. Use a 0.22 micron low-protein-binding in-line filter between the syringe and the infusion port. After infusion, flush the line with at least 10 mL of normal saline.
  • If platelet count at least 150,000/mm3, administer Y-90 Zevalin over 10 minutes as an intravenous infusion at a dose of Y-90 0.4 mCi per kg (14.8 MBq per kg) actual body weight.
  • If platelet count 100,000 to 149,000/mm3, in relapsed or refractory patients, administer Y-90 Zevalin over 10 minutes as an intravenous infusion at a dose of Y-90 0.3 mCi per kg (11.1 MBq per kg) actual body weight.
  • Do not administer more than 32 mCi (1184 MBq) Y-90 Zevalin dose regardless of the patient’s body weight.
• Monitor patients closely for evidence of extravasation during the infusion of Y-90 Zevalin. Immediately stop infusion and restart in another limb if any signs or symptoms of extravasation occur [see Warnings and Precautions (5.5)].

Directions for Preparation of Radiolabeled Y-90 Zevalin Doses

A clearly-labeled kit is required for preparation of Yttrium-90 (Y-90) Zevalin. Follow the detailed instructions for the preparation of radiolabeled Zevalin [see Dosage and Administration (2.4)].

Required materials not supplied in the kit:

1. Yttrium-90 Chloride Sterile Solution
2. Three sterile 1 mL plastic syringes
3. One sterile 3 mL plastic syringe
4. Two sterile 10 mL plastic syringes with 18-20 G needles
5. ITLC silica gel strips
6. 0.9% Sodium Chloride aqueous solution for the chromatography solvent
7. Developing chamber for chromatography
8. Suitable radioactivity counting apparatus
9. Filter, 0.22 micrometer, low-protein-binding
10. Appropriate acrylic shielding for reaction vial and syringe for Y-90

Method:

1. Allow contents of the refrigerated Y-90 Zevalin kit (Zevalin vial, 50 mM sodium acetate vial, and formulation buffer vial) to reach room temperature.
2. Place the empty reaction vial in an appropriate acrylic shield.
3. Determine the amount of each component needed:
   1. Calculate volume of Y-90 Chloride equivalent to 40 mCi based on the activity concentration of the Y-90 Chloride stock.
   2. The volume of 50 mM Sodium Acetate solution needed is 1.2 times the volume of Y-90 Chloride solution determined in step 3.a, above.
   3. Calculate the volume of formulation buffer needed to bring the reaction vial contents to a final volume of 10 mL.
4. Transfer the calculated volume of 50 mM Sodium Acetate to the empty reaction vial. Coat the entire inner surface of the reaction vial by gentle inversion or rolling.
5. Transfer 40 mCi of Y-90 Chloride to the reaction vial using an acrylic shielded syringe. Mix the two solutions by gentle inversion or rolling.
6. Transfer 1.3 mL of Zevalin (ibritumomab tiuxetan) to the reaction vial. Do not shake or agitate the vial contents.
7. Allow the labeling reaction to proceed at room temperature for 5 minutes. A shorter or longer reaction time may adversely alter the final labeled product.
8. Immediately after the 5-minute incubation period, transfer the calculated volume of formulation buffer from step 3.c. to the reaction vial. Gently add the formulation buffer down the side of the reaction vial. If necessary, withdraw an equal volume of air to normalize pressure.
9. Measure the final product for total activity using a radioactivity calibration system suitable for the measurement of Y-90.
10. Using the supplied labels, record the date and time of preparation, the total activity and volume, and the date and time of expiration, and affix these labels to the shielded reaction vial container.
11. Patient Dose: Calculate the volume required for a Y-90 Zevalin dose [see Dosage and Administration (2.2)]. Withdraw the required volume from the reaction vial. Assay the syringe in the dose calibrator suitable for the measurement of Y-90. The measured dose must be within 10% of the prescribed dose of Y-90 Zevalin and must not exceed 32 mCi (1184 MBq). Using the supplied labels, record the patient identifier, total activity and volume and the date and time of expiration, and affix these labels to the syringe and shielded unit dose container.
12. Determine Radiochemical Purity [see Dosage and Administration (2.4)].
13. Store Yttrium-90 Zevalin at 2-8°C (36-46°F) until use and administer within 8 hours of radiolabeling. Immediately prior to administration, assay the syringe and contents using a radioactivity calibration system suitable for the measurement of Y-90.

Procedure for Determining Radiochemical Purity

Use the following procedures for radiolabeling Y-90 Zevalin:

1. Place a small drop of Y-90 Zevalin at the origin of an ITLC silica gel strip.
2. Place the ITLC silica gel strip into a chromatography chamber with the origin at the bottom and the solvent front at the top. Allow the solvent (0.9% NaCl) to migrate at least 5 cm from the bottom of the strip. Remove the strip from the chamber and cut the strip in half. Count each half of the ITLC silica gel strip for one minute (CPM) with a suitable counting apparatus.
3. Calculate the percent RCP as follows:
   
   
4. Repeat the ITLC procedure if the radiochemical purity is <95%. If repeat testing confirms that radiochemical purity is <95%, do not administer the Y-90 Zevalin dose.

Radiation Dosimetry

During clinical trials with Zevalin, estimations of radiation-absorbed doses for Y-90 Zevalin were performed using sequential whole body images and the MIRDOSE 3 software program. The estimated radiation absorbed doses to organs and marrow from a course of the Zevalin therapeutic regimen are summarized in Table 1. Absorbed dose estimates for the lower large intestine, upper large intestine, and small intestine have been modified from the standard MIRDOSE 3 output to account for the assumption that activity is within the intestine wall rather than the intestine contents.