Xofigo Dosage

Generic name: RADIUM RA-223 DICHLORIDE 30uCi in 1mL
Dosage form: injection
Drug class: Therapeutic radiopharmaceuticals

Medically reviewed by Drugs.com. Last updated on Nov 30, 2023.

Recommended Dosage

The dose regimen of Xofigo is 55 kBq (1.49 microcurie) per kg body weight, given at 4 week intervals for 6 injections. Safety and efficacy beyond 6 injections with Xofigo have not been studied.

The volume to be administered to a given patient should be calculated using the:

•: Patient’s body weight (kg)
•: Dosage level 55 kBq/kg body weight or 1.49 microcurie/kg body weight
•: Radioactivity concentration of the product (1,100 kBq/mL; 30 microcurie/mL) at the reference date
•: Decay correction factor to correct for physical decay of radium-223.

The total volume to be administered to a patient is calculated as follows:

Volume to be administered (mL)	=	Body weight in kg × 55 kBq/kg body weight
		Decay factor × 1,100 kBq/mL

Volume to be administered (mL)	=	Body weight in kg × 1.49 microcurie/kg body weight
		Decay factor × 30 microcurie/mL

Table 1: Decay Correction Factor Table
Days from Reference Date	Decay Factor	Days from Reference Date	Decay Factor
-14	2.296	0	0.982
-13	2.161	1	0.925
-12	2.034	2	0.870
-11	1.914	3	0.819
-10	1.802	4	0.771
-9	1.696	5	0.725
-8	1.596	6	0.683
-7	1.502	7	0.643
-6	1.414	8	0.605
-5	1.330	9	0.569
-4	1.252	10	0.536
-3	1.178	11	0.504
-2	1.109	12	0.475
-1	1.044	13	0.447
		14	0.420
The Decay Correction Factor Table is corrected to 12 noon Central Standard Time (CST). To determine the decay correction factor, count the number of days before or after the reference date. The Decay Correction Factor Table includes a correction to account for the 7 hour time difference between 12 noon Central European Time (CET) at the site of manufacture and 12 noon US CST, which is 7 hours earlier than CET.

Immediately before and after administration, the net patient dose of administered Xofigo should be determined by measurement in an appropriate radioisotope dose calibrator that has been calibrated with a National Institute of Standards and Technology (NIST) traceable radium-223 standard (available upon request from Bayer) and corrected for decay using the date and time of calibration. The dose calibrator must be calibrated with nationally recognized standards, carried out at the time of commissioning, after any maintenance procedure that could affect the dosimetry and at intervals not to exceed one year.

Administration

Administer Xofigo by slow intravenous injection over 1 minute.

Flush the intravenous access line or cannula with isotonic saline before and after injection of Xofigo.

Discard any unused portion, if applicable [see Dosage and Administration (2.3)].

Instructions for Use/Handling

General warning

Xofigo (an alpha particle-emitting pharmaceutical) should be received, used and administered only by authorized persons in designated clinical settings. The receipt, storage, use, transfer and disposal of Xofigo are subject to the regulations and/or appropriate licenses of the competent official organization.

Xofigo should be handled by the user in a manner which satisfies both radiation safety and pharmaceutical quality requirements. Appropriate aseptic precautions should be taken.

Radiation protection

The administration of Xofigo is associated with potential risks to other persons (e.g., medical staff, caregivers and patient’s household members) from radiation or contamination from spills of bodily fluids such as urine, feces, or vomit. Therefore, radiation protection precautions must be taken in accordance with national and local regulations.1

For drug handling

Follow the normal working procedures for the handling of radiopharmaceuticals and use universal precautions for handling and administration such as gloves and barrier gowns when handling blood and bodily fluids to avoid contamination. In case of contact with skin or eyes, the affected area should be flushed immediately with water. In the event of spillage of Xofigo, the local radiation safety officer should be contacted immediately to initiate the necessary measurements and required procedures to decontaminate the area. A complexing agent such as 0.01 M ethylene-diamine-tetraacetic acid (EDTA) solution is recommended to remove contamination.

For patient care

Whenever possible, patients should use a toilet and the toilet should be flushed several times after each use. When handling bodily fluids, simply wearing gloves and hand washing will protect caregivers. Clothing soiled with Xofigo or patient fecal matter or urine should be washed promptly and separately from other clothing.

Radium-223 is primarily an alpha emitter, with a 95.3% fraction of energy emitted as alpha-particles. The fraction emitted as beta-particles is 3.6%, and the fraction emitted as gamma-radiation is 1.1%. The external radiation exposure associated with handling of patient doses is expected to be low, because the typical treatment activity will be below 8,000 kBq (216 microcurie). In keeping with the As Low As Reasonably Achievable (ALARA) principle for minimization of radiation exposure, it is recommended to minimize the time spent in radiation areas, to maximize the distance to radiation sources, and to use adequate shielding. Any unused product or materials used in connection with the preparation or administration are to be treated as radioactive waste and should be disposed of in accordance with local regulations.

The gamma radiation associated with the decay of radium-223 and its daughters allows for the radioactivity measurement of Xofigo and the detection of contamination with standard instruments.

Instructions for preparation

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

Xofigo is a ready-to-use solution and should not be diluted or mixed with any solutions. Each vial is for single use only.

Dosimetry

The absorbed radiation doses in major organs were calculated based on clinical biodistribution data in five patients with castration-resistant prostate cancer. Calculations of absorbed radiation doses were performed using OLINDA/EXM (Organ Level INternal Dose Assessment/EXponential Modeling), a software program based on the Medical Internal Radiation Dose (MIRD) algorithm, which is widely used for established beta and gamma emitting radionuclides. For radium-223, which is primarily an alpha particle-emitter, assumptions were made for intestine, red marrow and bone/osteogenic cells to provide the best possible absorbed radiation dose calculations for Xofigo, considering its observed biodistribution and specific characteristics. Additional particular modeling was applied for the lungs. The absorbed dose to the lungs is estimated as the dose contribution from 223Ra and daughter decays in the blood-containing fraction of the lung mass and also the dose contribution from 219Rn and daughter decays in the respiratory tract.

The calculated absorbed radiation doses to different organs per administered activity are listed in Table 2. The organs with highest absorbed radiation doses are bone (osteogenic cells), red marrow, and large intestine walls. The absorbed doses to other organs are lower.

Table 2: Absorbed Radiation Doses per Administered Activity
* LLI: lower large intestine; ULI: upper large intestine; colon dose = 0.57 × ULI dose + 0.43 × LLI dose2
Organ	Mean (mGy/MBq)	Mean (rad/mCi)	Coefficient of Variation (%)
Osteogenic cells	1152	4263	41
Red marrow	139	514	41
LLI wall*	46	172	83
Colon*	38	142	56
ULI wall*	32	120	50
Small intestine wall	7.3	27	45
Urinary bladder wall	4.0	15	63
Kidneys	3.2	12	36
Liver	3.0	11	36
Heart wall	1.7	6.4	42
Lungs	1.2	4.5	48
Ovaries	0.49	1.8	40
Uterus	0.26	0.94	28
Gallbladder wall	0.23	0.85	14
Stomach wall	0.14	0.51	22
Adrenals	0.12	0.44	56
Muscle	0.12	0.44	41
Pancreas	0.11	0.41	43
Brain	0.10	0.37	80
Spleen	0.09	0.33	54
Testes	0.08	0.31	59
Skin	0.07	0.27	79
Thyroid	0.07	0.26	96
Thymus	0.06	0.21	109
Breasts	0.05	0.18	120
Whole Body	23	86	16

More about Xofigo (radium 223 dichloride)

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Drug Status

Availability Prescription only Rx

Pregnancy & Lactation Risk data available

CSA Schedule* Not a controlled drug N/A

Approval History Drug history at FDA

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Pill medicine is Xofigo 1100 kBq/mL (30 microcurie/mL) with a total radioactivity of 6,600 kBq/vial (178 microcurie/vial) — Xofigo 1100 kBq/mL (30 microcurie/mL) with a total radioactivity of 6,600 kBq/vial (178 microcurie/vial)