GALLIUM CITRATE GA-67

GALLIUM CITRATE GA-67- gallium chloride ga-67 injection, solution
Curium US LLC

DESCRIPTION

Gallium Citrate Ga 67 Injection is supplied in a 10 milliliter vial as an isotonic, sterile, non-pyrogenic solution. Each milliliter of the isotonic solution contains 74 megabecquerels (2 millicuries) of gallium Ga-67 on the calibration date as a complex formed from 8.3 nanograms gallium chloride Ga-67, 1.9 milligrams of sodium citrate dihydrate, 7.8 milligrams of sodium chloride and 0.9 percent benzyl alcohol (v/v) as a preservative. The pH is adjusted to between 5.5 to 8.0 with hydrochloric acid and/or sodium hydroxide solution.

Gallium Ga-67, with a half-life of 78.26 hours, is cyclotron produced by the proton irradiation of enriched zinc. At the time of calibration the drug contains no more than 0.02% gallium Ga-66 and no more than 0.2% zinc Zn-65. The concentration of each radionuclidic impurity changes with time. At expiration, the drug contains no more than 0.001% gallium Ga-66 and no more than 1.0% zinc Zn-65. No carrier has been added.

Gallium citrate has the following chemical structure:

Chemical Structure
(click image for full-size original)

Physical Characteristics

Gallium Ga-67 with a physical half-life of 78.26 hours 1decays by electron capture to stable zinc Zn-67. Photons that are useful for imaging studies are listed in Table 1.

Table 1. Principal Radiation Emission Data
Radiation Mean Percent PerDisintegration Energy(keV)
Gamma-2 2.9 91.3
Gamma-3 35.7 93.3
Gamma-4 19.7 184.6
Gamma-5 2.2 209.0
Gamma-6 16.0 300.2
Gamma-7 4.5 393.5

1
Kocher, D.C., Radioactive Decay Data Tables, Health and Safety Research Division, National Technical Information Service, DOE/TIC-11026, pg. 80, 1981.

External Radiation

The specific gamma ray constant for gallium Ga-67 is 1.6 R/mCi-hour at 1 cm. The first half-value thickness of lead (Pb) is 0.066 cm. A range of values for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of lead is shown in Table 2. For example, the use of 1.2 cm of lead will decrease the radiation exposure by a factor of about 100.

Table 2. Radiation Attenuation by Lead Shielding

Shield Thickness (Pb), cm

Coefficient of Attenuation

0.066

0.41

1.2

2.5

4.8

0.5

10-1

10-2

10-3

10-4

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. Physical Decay Chart; Gallium Ga-67, Half-Life 78.26 Hours

Hours

Fraction Remaining

Hours

Fraction Remaining

0*

6

12

18

24 (1d)

30

36

42

48 (2d)

54

60

66

1.000

0.948

0.899

0.853

0.809

0.767

0.727

0.689

0.654

0.620

0.588

0.557

72 (3d)

78

84

90

96 (4d)

108

120 (5d)

132

144 (6d)

156

168 (7d)

0.529

0.501

0.475

0.451

0.427

0.384

0.345

0.311

0.279

0.251

0.226

* Calibration Time

CLINICAL PHARMACOLOGY

Gallium Citrate Ga 67, with no carrier added, has been found to concentrate in certain viable primary and metastatic tumors as well as focal sites 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 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 Ga-67 is excreted relatively slowly from the body. The average whole body retention is 65 percent after seven days, with 26 percent having been excreted in the urine and 9 percent in the stools.

INDICATIONS AND USAGE

Gallium Citrate Ga 67 Injection may be useful to demonstrate the presence and extent of Hodgkin’s disease, lymphoma, and bronchogenic carcinoma. Positive gallium 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.

WARNINGS

None known.

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 states. The finding of an abnormal gallium Ga-67 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 as well as focal areas of infection. Certain pathologic conditions may yield up to 40 percent false negative gallium Ga-67 studies. Therefore, a negative study cannot be definitely 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.

As in the use of any radioactive material, care should be taken to minimize radiation exposure to the patient consistent with proper management and to ensure minimum radiation exposure to occupational workers.

The vial contents are sterile and non-pyrogenic. It is essential that the user follow the directions carefully and adhere to strict aseptic procedures.

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

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