PRECAUTIONS: Data are not available concerning the effect of marked alterations in blood glucose, insulin, or pH (such as is found in diabetes mellitus) on the quality of Thallous Chloride TI 201 Injection scans. Attention is directed to the fact that thallium is a potassium analog, and since the transport of potassium is affected by these factors, the possibility exists that the thallium may likewise be affected. General Do not use after the expiration time and date (5 days maximum after calibration time) stated on the label. Do not use if contents are turbid. The patient dose should be measured by a suitable radioactivity calibration system immediately prior to administration. Thallous Chloride TI 201 Injection, as all radioactive materials, must be handled with care and used with appropriate safety measures to minimize external radiation exposure to clinical personnel. Care should also be taken to minimize radiation exposure to patients in a manner 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. Carcinogenesis, Mutagenesis, Impairment of Fertility No long-term animal studies have been performed to evaluate carcinogenic potential, mutagenic potential, or whether Thallous Chloride Tl 201 Injection affects fertility in males or females. Ideally, examinations using radiopharmaceuticals, especially those elective in nature, of a woman of child-bearing capability should be performed during the first few (approximately 10) days following the onset of menses. Pregnancy Adequate reproductive studies have not been conducted in animals with Thallous Chloride Tl 201 Injection. It is also not known whether Thallous Chloride TI 201 Injection can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Thallous Chloride Tl 201 Injection should not be given to a pregnant woman except when benefits clearly outweigh the potential risks. Nursing Mothers It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, nursing should not be undertaken when a patient is administered radioactive material. Pediatric Use Safety and effectiveness in the pediatric population has not been established. Geriatric Use Clinical studies of Thallous Chloride TI 201 Injection did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. 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.