technetium Tc-99m tetrofosmin

Action and Spectrum

Actions and Spectrum: 

The mechanism of action of technetium Tc-99m tetrofosmin is based on its ability to mimic the behavior of certain molecules in the body, allowing imaging of specific physiological processes. Tc-99m tetrofosmin is designed to be taken up by cardiac muscle cells in proportion to blood flow, making it particularly useful for myocardial perfusion imaging. 

When administered intravenously, Tc-99m tetrofosmin is rapidly distributed in the bloodstream and reaches the heart. It enters myocardial cells proportionately to regional blood flow and is then retained in these cells due to its lipophilic nature.

The retention of the radiotracer in the myocardium is influenced by factors such as cell membrane integrity, blood flow, and metabolic activity. Areas with reduced blood flow, such as those affected by ischemia or infarction, exhibit decreased uptake and retention of Tc-99m tetrofosmin, leading to visual differences in imaging scans. 

Drug Interaction

Adverse Reaction

Frequency defined 

1-10% 

Leukocytosis 

<1% 

Allergic skin reaction 

Angina pectoris 

Dyspnea 

Hypersensitivity reaction 

Abdominal distress 

Altered sense of smell 

Burning sensation in the mouth 

Fever 

Black Box Warning

Black box warning: 

None 

Contraindication / Caution

Contraindications/caution: 

Contraindications: 

None 

Caution: 

• Radiation Exposure: Tc-99m tetrofosmin is a radioactive substance, and patients receive a small amount of radiation during imaging.  
• Allergies and Sensitivities: Patients should inform their healthcare providers if they have a history of allergies, sensitivities, or adverse reactions to any medications or substances, including radiopharmaceuticals. 

Pregnancy / Lactation

Pregnancy consideration: There is a greater risk of fetal damage when radiopharmaceuticals are administered at high dosages. 

Lactation: Excretion of the drug in human breast milk is known 

Pregnancy category: 

Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester. 

Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 

Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    

Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    

Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    

Category N: There is no data available for the drug under this category 

Pharmacology

Pharmacology: 

After intravenous administration, technetium Tc-99m tetrofosmin rapidly enters the bloodstream. It is distributed throughout the body, with a significant proportion accumulating in specific tissues based on physiological characteristics. The primary target tissue for Tc-99m tetrofosmin imaging is the myocardium (heart muscle cells), whose uptake is proportional to blood flow. 

In the myocardium, Tc-99m tetrofosmin is taken up by cardiac cells, particularly those with intact cell membranes and sufficient metabolic activity. The radiotracer’s lipophilic nature contributes to its retention in these cells. This localization of Tc-99m tetrofosmin in myocardial tissue forms the basis for its application in myocardial perfusion imaging. 

• Myocardial Perfusion Imaging: Tc-99m tetrofosmin’s behavior in the myocardium allows for non-invasive myocardial perfusion imaging. The radiotracer accumulates in areas of the heart with normal blood flow, and its distribution reflects healthy tissue perfusion. In regions with reduced blood flow, such as those affected by coronary artery disease or ischemia, the uptake and retention of Tc-99m tetrofosmin are diminished, creating detectable differences in imaging scans.  
• Retention and Clearance: The retention of Tc-99m tetrofosmin in the myocardium is related to factors like blood flow, cellular integrity, and metabolic activity. Areas with compromised blood flow or damaged cells tend to exhibit reduced radiotracer accumulation. 

Pharmacodynamics:  

The pharmacodynamics of technetium Tc-99m tetrofosmin are centered around its uptake, retention, and emission of gamma radiation within tissues, particularly the myocardium. Its ability to provide valuable diagnostic information through non-invasive imaging makes it a valuable tool in nuclear medicine, especially for myocardial perfusion imaging and blood flow and tissue viability assessment. 

Pharmacokinetics: 

Absorption 

Tc-99m tetrofosmin is administered intravenously, typically as an injection into a vein. It doesn’t undergo the same absorption processes as a radiotracer as traditional drugs. Upon injection, it directly enters the bloodstream and rapidly distributes throughout the body. 

Distribution 

technetium Tc-99m tetrofosmin is distributed in various tissues within the body after intravenous administration. The distribution includes: 

• Myocardium: Tc-99m tetrofosmin is taken up by cardiac muscle cells in proportion to blood flow, making it a valuable radiotracer for myocardial perfusion imaging. 
• Blood: It initially circulates in the bloodstream, allowing it to reach various organs and tissues. 
• Liver: Some amount of Tc-99m tetrofosmin is distributed to the liver. 
• Lung: It is also distributed to the lung tissue. 

Metabolism 

Tc-99m tetrofosmin doesn’t undergo significant metabolic transformations in the body. It retains its chemical structure and properties during its time in the body.  

Elimination and Excretion 

The physical half-life of Tc-99m is approximately 6.03 hours. This relatively short half-life allows for practical imaging without prolonged radiation exposure. It takes for Tc-99m tetrofosmin to reach peak myocardial uptake, which is the highest accumulation level in cardiac muscle cells, approximately 5 minutes. This rapid uptake and retention contribute to its suitability for myocardial perfusion imaging. 

Tc-99m tetrofosmin is eliminated from the body through both urine and feces. Approximately 40% of the injected activity is excreted in the urine within 48 hours after administration. Around 26% of the injected activity is also excreted in the feces within the same time frame. This excretion process helps reduce the radiation exposure to the patient over time. 

Adminstartion

Administration: 

Intravenous administration 

The typical administration process for Tc-99m tetrofosmin: 

• Patient Preparation: Patients undergoing technetium Tc-99m tetrofosmin imaging usually need to fast for a specific period before the procedure, often for several hours. This fasting helps improve the accuracy of the imaging results. 
• Radiotracer Injection: technetium Tc-99m tetrofosmin is prepared as a sterile, pyrogen-free solution for injection. Administer the radiotracer via an intravenous (IV) line. The injection is typically done in a vein, often in the arm. The injection process is usually quick and relatively painless. 
• Waiting Period: After the injection, there is a brief period to allow the radiotracer to circulate throughout the body and localize in the target tissues. This waiting period may vary depending on the specific imaging protocol and the area of interest. 
• Imaging Procedure: Once the waiting period is over and the radiotracer is adequately distributed in the body, the patient undergoes imaging. The imaging uses specialized equipment, such as a gamma camera or a SPECT (single-photon emission computed tomography) scanner. These devices detect the gamma radiation emitted by the Tc-99m tetrofosmin and create images of its distribution in the body. For myocardial perfusion imaging, multiple images are often acquired from different angles to view the heart’s blood flow comprehensively. 
• Post-Imaging: After the imaging session, the patient is typically free to resume normal activities. Depending on the specific protocol and the facility’s policies, the patient may be required to take certain precautions to minimize radiation exposure to others.  
• Data Analysis and Reporting: The acquired images are analyzed by trained medical professionals, often nuclear medicine physicians or radiologists. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: technetium Tc-99m tetrofosmin 

Why do we use technetium Tc-99m tetrofosmin? 

technetium Tc-99m tetrofosmin is widely used in nuclear medicine for various diagnostic imaging procedures. Its applications primarily focus on assessing blood flow, tissue viability, and physiological processes within the body. Some of the key uses of Tc-99m tetrofosmin include: 

• Myocardial Perfusion Imaging (MPI): This is one of the primary applications of Tc-99m tetrofosmin. It is used to assess blood flow to the heart muscle, helping to diagnose coronary artery disease, myocardial infarction (heart attack), and ischemia (reduced blood flow to the heart). MPI provides information about blood flow distribution within the heart and helps identify areas with compromised perfusion. 
• Cardiac Viability Assessment: Tc-99m tetrofosmin can help determine cardiac tissue viability, particularly after a heart attack. It assists in identifying regions of the heart that are still functional and can recover with appropriate interventions. 
• Brain Perfusion Imaging: Tc-99m tetrofosmin can be used to assess blood flow in the brain. It helps diagnose conditions such as cerebrovascular disease, ischemia, and brain tumors. Visualizing blood flow patterns provides insights into brain health and potential abnormalities. 
• Parathyroid Imaging: Tc-99m tetrofosmin is utilized to locate abnormal parathyroid glands in hyperparathyroidism, a condition characterized by the overactivity of these glands. The radiotracer helps pinpoint the exact location of overactive parathyroid tissue for surgical planning. 
• Bone Imaging (Scintigraphy): Tc-99m tetrofosmin is sometimes used for skeletal scintigraphy to assess bone health and detect conditions such as bone metastases, fractures, infections, and certain bone disorders. 
• Detection of Metastases: In some cases, Tc-99m tetrofosmin can detect metastatic cancer cells that have spread to the lymph nodes or other tissues. The radiotracer’s distribution patterns can provide valuable information about the presence and extent of metastases.