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Thallous Chloride

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Thallous Chloride Tl-201 Injection

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Thallous Chloride Tl-201 may be useful in myocardial perfusion imaging using either planar or SPECT (Single Photon Emission Computed Tomography) techniques for the diagnosis and localization of myocardial infarction. It may also have prognostic value regarding survival, when used in the clinically stable patient following the onset of symptoms of an acute myocardial infarction, to assess the site and size of the perfusion defect.

Thallous Chloride Tl-201 may also be useful in conjunction with exercise stress testing as an adjunct to the diagnosis of ischemic heart disease (atherosclerotic coronary artery disease).

Thallous Chloride Tl-201 is also indicated for scintigraphic imaging of the myocardium to identify changes in perfusion induced by pharmacologic stress in patients with known or suspected coronary artery disease and who cannot exercise adequately.

It is usually not possible to differentiate recent from old myocardial infarction, or to differentiate exactly between recent myocardial infarction and ischemia.

Thallous Chloride Tl-201 is indicated also for the localization of sites of parathyroid hyperactivity in patients with elevated serum calcium and parathyroid hormone levels. It may also be useful in preoperative screening to localize extrathyroidal and mediastinal sites of parathyroid hyperactivity and for postsurgical reexamination. Thallous Chloride Tl-201 has not been adequately demonstrated to be effective for the localization of normal parathyroid glands.


The recommended adult dose of intravenous Thallous Chloride Tl-201 for planar myocardial imaging is 37 to 74 MBq (1 to 2 mCi). The recommended intravenous doses for SPECT myocardial imaging are 74 to 111 MBq (2 to 3 mCi). The efficacy of a 1.0 mCi dose for SPECT imaging has not been well established.

For the localization of parathyroid hyperactivity, Thallous Chloride Tl-201 may be administered before, with or after a minimal dose of a thyroid imaging agent such as sodium pertechnetate Tc 99m or sodium iodide I-123 to enable thyroid subtraction imaging.

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit. Do not use if contents are turbid.

Waterproof gloves should be worn during the handling procedures.

The patient dose should be measured by a suitable radioactivity calibration system immediately prior to administration.

With a shielded sterile syringe, aseptically withdraw the material for use.

For resting Thallous Chloride Tl-201 studies, imaging should begin 10 to 20 minutes after injection. Myocardial-to-background ratios are improved when patients are injected upright and in the fasting state; the upright position reduces the hepatic and gastric Thallium Tl-201 concentration.

When utilized in conjunction with exercise stress testing, Thallous Chloride Tl-201 should be administered at the inception of a period of maximum stress which is sustained for approximately 30 seconds after injection. Imaging should begin within ten minutes after administration to obtain maximum target-to-background ratios. Several investigators have reported that within two hours after the completion of stress testing the target-to-background ratios may decrease significantly in lesions that are attributable to transient ischemia.

Radiation Dosimetry

The estimated absorbed radiation doses4 at calibration time to an average patient (70 kg) from an intravenous injection of Thallous Chloride Tl-201 are shown in Table 4.

Table 4. Radiation Dose Estimates for Tl-201 Chloride (plus contaminants)

  Estimated Radiation Dose
Organ mGy/MBq rad/mCi
Adrenals 6.2E-02 2.3E-01
Brain 5.9E-02 2.2E-01
Breasts 3.6E-02 1.3E-01
GB Wall 8.3E-02 3.1E-01
LLI Wall 3.4E-01 1.2E+00
Small Intestine 4.5E-01 1.7E+00
Stomach 1.9E-01 6.9E-01
ULI Wall 3.3E-01 1.2E+00
Heart Wall 2.8E-01 1.0E+00
Kidneys 4.6E-01 1.7E+00
Liver 9.9E-02 3.7E-01
Lungs 4.7E-02 1.7E-01
Muscle 4.6E-02 1.7E-01
Ovaries 1.0E-01 3.7E-01
Pancreas 7.4E-02 2.7E-01
Red Marrow 5.5E-02 2.0E-01
Bone Surfaces 8.8E-02 3.3E-01
Skin 3.3E-01 1.2E-01
Spleen 1.8E-01 6.5E-01
Testes 8.2E-01 3.0E+00
Thymus 4.6E-02 1.7E-01
Thyroid 6.2E-01 2.3E+00
Urinary Bladder Wall 5.2E-02 1.9E-01
Uterus 8.5E-02 3.1E-01
Effective Dose Equivalent 3.6E-01/mSv/MBq 1.3E+00 rem/mCi

Based on data gathered in humans by Krahwinkel et al. (J Nucl Med 29 (9):1582-1586, 1988) and data gathered in humans by Gupta et al (Int J Nucl Med & Biol 8:211-213, 1981).

Table 5. Assumed Distribution and Retention

Brain 1.76% Tb =∞  
LLI 3.6% Tb = 191 hr (Activity in Wall)
Small Intestine 14.4% Tb =191hr (Activity in Wall)
Stomach 2.8% Tb =205hr (Activity in Wall)
ULI 4.7% Tb = 191hr (Activity in Wall)
Heart Wall 3.4% Tb =179hr  
Kidneys 4.5% Tb =260hr 0.97% Tb = 27 hr
Liver 4.6% Tb =218hr  
Spleen 0.74% Tb =640hr 0.28% Tb = 37 hr
Testes 1.0% Tb =∞  
Thyroid 0.29% Tb =350hr 0.24% Tb = 166hr
TotalBody 31% Tb =146hr 69% Tb = 502hr
Urinary Bladder Clearance 6.2% Tb =146hr 13.8% Tb = 502hr

Bladder voiding interval 4.8 hr. Contaminants assumed: Tl-200 (1%), Tl-202 (0.33%), Pb-201 (0.33%), Pb-203 (0.33%). Includes dose from Tl-201 Auger electrons. Estimate calculated using phantom of Cristy & Eckerman (Report ORNL/TM-8381/V1 & V7) Radiation Internal Dose Information Center


Catalog Number 120: NDC No. 0019-N120-28, NDC No. 0019-N120-56, NDC No. 0019-N120-63, NDC No. 0019-N120-99.

Thallous Chloride Tl-201 is supplied in a sterile, non-pyrogenic solution for intravenous administration. Each mL contains 37 MBq (1 mCi) Thallous Chloride Tl-201 at calibration time, 9 mg sodium chloride and 0.9 percent (v/v) benzyl alcohol. The pH is adjusted to between 4.5 to 7.0 with hydrochloric acid and/or sodium hydroxide solution. Vials are available in the following quantities of radioactivity: 103.6, 207.2, 233.1, 366.3 megabecquerels (2.8, 5.6, 6.3 and 9.9 millicuries) of thallium Tl-201.

The contents of the vial are radioactive. Adequate shielding and handling precautions must be maintained.

Storage Conditions

Store this drug at controlled room temperature, 20° to 25°C (68° to 77°F) [see USP].

Storage and disposal of Thallous Chloride Tl-201 Injection (thallous chloride) should be controlled in a manner that is in compliance with the appropriate regulations of the government agency authorized to license the use of this radionuclide.


4. Values listed include an average maximum correction of 6 percent to the radiation doses from Thallium Tl-201 due to the radiocontaminants Thallium Tl-200 and Thallium Tl-202 on calibration date.

Mallinckrodt Inc. St. Louis, MO 63134. Rev 101906. FDA Rev date: n/a

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 10/21/2008

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