Gallium Citrate Ga 67

GALLIUM CITRATE GA 67- gallium citrate, ga-67 injection, solution
Bristol-Myers Squibb Medical Imaging

FOR DIAGNOSTIC USE

DESCRIPTION: Gallium Citrate Ga 67 Injection is supplied in isotonic solution as a sterile, non-pyrogenic diagnostic radiopharmaceutical for intravenous administration. Each milliliter of the isotonic solution contains 74 MBq (2 mCi) of Gallium Ga 67 on the calibration date, as a complex formed from 9 ng Gallium Chloride Ga 67, 2 mg of sodium citrate, 6.8 mg sodium chloride, and 9 mg benzyl alcohol/mL added as preservative. The pH is adjusted to between 4.5-8 with hydrochloric acid and/or sodium hydroxide solution. Gallium Ga 67, with a half-life of 78.3 hours, is cyclotron produced by the proton irradiation of enriched zinc oxide, is essentially carrier-free and contains negligible concentrations of other radioactive isotopes.

The radionuclidic composition at calibration time is ≥99.89% Gallium Ga 67, ≤0.01% Gallium Ga 66 and ≤0.1% due to other radiocontaminants, each expressed as a percentage of total activity. The radionuclidic composition at expiration time is ≥99.89% Gallium Ga 67, essentially zero (0.0002%) Gallium Ga 66 and essentially zero of other radiocontaminants each expressed as a percentage of total activity.

The chemical structure for Gallium Citrate is shown below:

Image from Drug Label Content

PHYSICAL CHARACTERISTICS

Gallium Ga 67 decays to stable Zinc Zn 67 by electron capture with a physical half-life of 78.3 hours.1

TABLE 1. Principal Radiation Emission Data
Radiation Mean %/Disintegration Mean Energy (keV)
1 Kocher, David C., “Radioactive Decay Data Tables”, DOE/TIC-11026 (1981).
Gamma-3 35.7 93.3
Gamma-4 19.7 184.6
Gamma-6 16.0 300.2

EXTERNAL RADIATION

The specific gamma ray constant for Gallium Ga 67 is 5.58 microcoulombs/Kg-hr-MBq (0.80R/hr-mCi) at 1 cm. The first half value thickness of lead is 0.066 cm. A range of values for the relative attenuation of the radiation emitted by this radionuclide that results from the interposition of various thicknesses of Pb is shown in Table 2. For example, the use of 0.41 cm of Pb will decrease the external radiation exposure by a factor of 10.

TABLE 2. Radiation Attenuation By Lead Shielding
cm of Lead (Pb) RadiationAttenuation Factor cm of Lead (Pb) RadiationAttenuation Factor
0.066 0.5 2.5 10-3
0.41 10-1 4.8 10-4
1.2 10-2

To correct for physical decay of this radionuclide, the fractions that remain at selected time intervals after the time of calibration are shown in Table 3.

TABLE 3. Gallium Ga 67 Decay Chart Half-Life 78.3 Hours
Hours FractionRemaining Hours FractionRemaining Hours FractionRemaining
*Calibration Time
0* 1.00 42 0.69 84 0.48
6 0.95 48 0.65 90 0.45
12 0.90 54 0.62 96 0.43
18 0.85 60 0.59 108 0.38
24 0.81 66 0.56 120 0.35
30 0.77 72 0.53 132 0.31
36 0.73 78 0.50 144 0.28
156 0.25
168 0.23

CLINICAL PHARMACOLOGY: Carrier-free Gallium Citrate Ga 67 Injection has been found to concentrate in certain viable primary and metastatic tumors, as well as focal site of infection. The mechanism of concentration is unknown, but investigational studies have shown that Gallium Ga 67 accumulates in lysosomes and is bound to a soluble intracellular protein.

It has been reported in the scientific literature that following intravenous injection, the highest tissue concentration of Gallium Ga 67 – other than tumors and sites of infection– is in the renal cortex. After the first day, the maximum concentration shifts to bone and lymph nodes, and after the first week, to liver and spleen. Gallium is excreted relatively slowly from the body. The average whole body retention is 65% after 7 days, with 26% having been excreted in the urine and 9% in the stools.

INDICATIONS AND USAGES: Gallium Citrate Ga 67 Injection may be useful in demonstrating the presence of the following malignancies: Hodgkins disease, lymphomas and bronchogenic carcinoma. Positive Ga 67 uptake in the absence of prior symptoms warrants follow-up as an indication of a potential disease state.

Gallium Citrate Ga 67 Injection may be useful as an aid in detecting some acute inflammatory lesions.

CONTRAINDICATIONS: None known.

WARNINGS: Because of the benzyl alcohol content, caution should be used in administration to newborns, particularly infants born prematurely, and individuals with impaired liver function.

PRECAUTIONS

General

A thorough knowledge of the normal distribution of intravenously administered Gallium Citrate Ga 67 Injection is essential in order to accurately interpret pathologic studies.

The finding in an abnormal gallium concentration usually implies the existence of underlying pathology, but further diagnostic studies should be done to distinguish benign from malignant lesions. Gallium Citrate Ga 67 Injection is intended for use as an adjunct in the diagnosis of certain neoplasms. Certain pathologic conditions may yield up to 40% false negative gallium studies. Therefore, a negative study cannot be definitively interpreted as ruling out the presence of disease.

Lymphocytic lymphoma frequently does not accumulate Gallium Ga 67 sufficiently for unequivocal imaging; and the use of gallium with this histologic type of lymphoma is not recommended at this time.

Gallium Ga 67 localization cannot differentiate between tumor and acute inflammation; and other diagnostic studies must be added to define the underlying pathology.

Gallium Citrate Ga 67 Injection, as well as any other radioactive drugs, must be handled with care, and appropriate safety measures should be used to minimize external radiation exposure to clinical personnel. Care should also be taken to minimize radiation exposure to patients consistent with proper patient management.

Radiopharmaceuticals should be used only by physicians who are qualified by training and experience in the safe use and handling of radionuclides and whose experience and training have been approved by the appropriate government agency authorized to license the use of radionuclides.

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