CLINICAL PHARMACOLOGY SECTION

CLINICAL PHARMACOLOGY

Indium forms a saturated (1:3) complex with oxyquinoline. The complex is neutral and lipid-soluble, which enables it to penetrate the cell membrane. Within the cell, indium becomes firmly attached to cytoplasmic components; the liberated oxyquinoline is released by the cell. It is thought likely that the mechanism of labeling cells with Indium In 111 Oxyquinoline Solution involves an exchange reaction between the oxyquinoline carrier and subcellular components which chelate indium more strongly than oxyquinoline. The low stability constant of the oxyquinoline complex, estimated at approximately 10, supports this theory.

Following the recommended leukocyte cell labeling procedure, approximately 77% of the added indium In 111 oxyquinoline is incorporated in the resulting cell pellet (which represents approximately 3 to 4 × 108 WBC).

Cell clumping can occur and was found in about one fifth of the leukocyte preparations examined. The presence of red blood cells or plasma will lead to reduced leukocyte labeling efficiency. Transferrin in plasma competes for indium In 111 oxyquinoline.

After injection of labeled leukocytes into normal volunteers, about 30% of the dose is taken up by spleen and 30% by liver, reaching a plateau at 2 to 48 hours after injection. No significant clearance of radioactivity is observed at 72 hours in these two organs. Pulmonary uptake is 4 to 7.5% at 10 minutes but is lost rapidly; pulmonary radioactivity is usually visible in scans only up to about 4 hours after injection.

The human biodistribution studies in three normal subjects injected with indium In 111 oxyquinoline labeled leukocytes indicate a biexponential disappearance of indium In 111 from the blood when monitored for up to 72 hours. Between 9.5 to 24.4% of the injected dose remains in whole blood and clears with a biological half-time of 2.8 to 5.5 hours. The remainder (13 to 18%) clears from blood with a biological half-time of 64 to 116 hours.

Elimination from the body of injected indium In 111 oxyquinoline is probably mainly through decay to stable cadmium since only a negligible amount (less than 1%) of the dose is excreted in feces and urine in 24 hours.

Clearance from whole blood and biological distribution can vary considerably with the individual recipient, the condition of the injected cells and labeling techniques used.

Release of radioactivity from the labeled cells is about 3% at 1 hour and 24% at 24 hours.

Clearance from liver and spleen, for the purpose of calculating the radiation dose, is assumed to be equal to the physical half-life of indium In 111 (67.9 hours).

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PRECAUTIONS SECTION

PRECAUTIONS

Clumping of cells may produce focal accumulations of radioactivity in lungs which do not wash out in 24 hours and thus may lead to false positive results. This phenomenon can be detected by imaging the chest immediately after injection.

The normally high uptake of indium In 111 oxyquinoline labeled leukocytes by spleen and liver may mask inflammatory lesions in these organs. Labeled leukocytes have been observed to accumulate in the colon and accessory spleens of patients with or without disease.

Chemotaxis of granulocytes deteriorates during storage and loss of chemotaxis may cause false negative scans. The spontaneous release of indium In 111 has been reported to range from about 3% at one hour to 24% at 24 hours [ten Berge, R.J.M., Natarajan, A.T., Hardeman, M.R., et al, Labeling with indium In 111 has detrimental effects on human lymphocytes, Journal of Nuclear Medicine, 24, 615-620 (1983)]. The maximum amount of time recommended between drawing the blood and reinjection should not exceed 5 hours. It is recommended that the labeled cells be used within one hour of preparation, if possible and in no case more than three hours after preparation.

Plasma and red cell contamination impairs labeling efficiency of leukocytes. Hemolyzed blood in labeled leukocytes may produce heart pool activity and should be avoided.

Cell aggregates of various degrees have been reported. Cell labeling techniques and standing of cell preparation may be contributing factors.

Nuclear medicine procedures involving withdrawal and reinjection of blood have the potential for transmission of blood borne pathogens. Procedures should be implemented to avoid administration errors and viral contamination of personnel during blood product labeling. A system of checks similar to the ones used for administering blood transfusions should be routine.

General

Strict aseptic techniques should be used to maintain sterility throughout the procedures for using this product.

Do not use after the expiration time and date (5 days after calibration time) stated on the label.

The contents of the vial are radioactive. Adequate shielding of the preparation must be maintained at all times.

Indium In 111 Oxyquinoline Solution, like other radioactive drugs, must be handled with care and appropriate safety measures should be used to minimize radiation exposure to clinical personnel. Care should also be taken to minimize radiation exposure to the patient 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 governmental agency authorized to license the use of radionuclides.

Carcinogenesis, Mutagenesis, Impairment of Fertility

Although earlier studies suggested that oxyquinoline (oxine) might have carcinogenic potential, recent studies have found no evidence of carcinogenicity in either rats or mice given oxyquinoline in feed at concentrations of 1,500 or 3,000 ppm for 103 weeks.

It has been reported [ten Berge, R.J.M., Natarajan, A.T., Hardeman, M.R., et al, Labeling with indium In 111 has detrimental effects on human lymphocytes, Journal of Nuclear Medicine, 24, 615-620 (1983)] that human lymphocytes labeled with recommended concentrations of indium In 111 oxyquinoline showed chromosome aberrations consisting of gaps, breaks and exchanges that appear to be radiation induced. At 555 kBq/107, 15 µCi/107 lymphocytes 93% of the cells were reported to be abnormal. The oncogenic potential of such lymphocytes has not been studied. It has been reported that the radiation dose to 108 leukocytes is 9 × 104 mGy (0.9 × 104 rads) from 18.5 MBq, 500 µCi [Goodwin, David A., Cell labeling with oxine chelates of radioactive metal ions: Techniques and clinical implications, Journal of Nuclear Medicine, 19, 557-559 (1978)].

Studies have not been performed to evaluate whether indium In 111 oxyquinoline affects fertility in male or female laboratory animals or humans.

Pregnancy

Animal reproduction studies have not been conducted with indium In 111 oxyquinoline labeled leukocytes. It is also not known whether indium In 111 oxyquinoline labeled leukocytes can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity.

However, Indium Nitrate, a closely related compound, was teratogenic and embryopathic in hamsters. Indium In 111 oxyquinoline labeled leukocytes should be given to a pregnant woman only if clearly needed.

Ideally, examinations using radiopharmaceuticals, especially those elective in nature, in women of childbearing capability should be performed during the first few (approximately ten) days following the onset of menses.

Nursing Mothers

It is reported that indium 111 is secreted in human milk following administration of indium In 111 labeled leukocytes. Therefore, formula feedings should be substituted for breast feedings.

Pediatric Use

Safety and effectiveness in pediatric patients below age 18 have not been established (See Warnings).

Geriatric Use

Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

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