Tc-99m Tetrofosmin
Tc-99m Tetrofosmin Uses, Dosage, Side Effects, Food Interaction and all others data.
Tc-99m Tetrofosmin is a drug used in nuclear myocardial perfusion imaging. The radioisotope, technetium-99m, is chelated by two 1,2-bis[di-(2-ethoxyethyl)phosphino]ethane ligands which belong to the group of diphosphines and which are referred to as tetrofosmin. It is a lipophilic technetium phosphine dioxo cation that was formulated into a freeze-dried kit which yields an injection. Tc-99m Tetrofosmin was developed by GE Healthcare and FDA approved on February 9, 1996.
Preclinical studies have reported that technetium-99m tetrofosmin presents a very good heart uptake and retention. The diagnosis based on the presence of technetium-99m is considered to have a principal photon gamma emissions at 140.5 keV. The imaging can be done at 15 minutes after stress and 30-60 minutes at rest but, due to its slow wash out from myocardium, it is possible to perform imaging for up to 4 hours post-injection. Administration of technetium-99m tetrofosmin generates a count elevation in white blood cell at 6-24 hours post-injection.
| Trade Name | Tc-99m Tetrofosmin |
| Generic | Technetium Tc-99m tetrofosmin |
| Technetium Tc-99m tetrofosmin Other Names | Tc-99m tetrofosmin, Technetium (99mTc) tetrofosmin, Technetium Tc 99m tetrofosmin, Technetium-99 tetrofosmin |
| Type | |
| Formula | C36H84O10P4Tc |
| Weight | Average: 898.86 Monoisotopic: 898.408712589 |
| Protein binding | The protein binding of technetium-99m tetrofosmin has not been assessed, but it is thought that the uptake of this drug may be related to its binding to P-glycoprotein and multidrug resistance proteins. |
| Groups | Approved |
| Therapeutic Class | |
| Manufacturer | |
| Available Country | |
| Last Updated: | September 19, 2023 at 7:00 am |
Uses
Technetium-99m tetrofosmin is indicated for the diagnosis of heart abnormalities by exercise myocardial scintigraphy. The exercise myocardial scintigraphy is an established method for the diagnosis of the severity of coronary artery disease. This method allows distinguishing regions of reversible myocardial ischemia in the presence or absence of infarcted myocardium following rest and stress conditions. The use of technetium-99m tetrofosmin is mainly used to assess myocardial perfusion in ischemia and infarction.
How Tc-99m Tetrofosmin works
The mechanism for the uptake and retention of technetium-99m tetrofosmin is not well established. Nonetheless, it is known that technetium 99m tetrofosmin binds to the intracellular cytosol of myocytes. This uptake is thought to be because technetium-99m tetrofosmin is a lipophilic cationic agent which allows it to present a passive diffusion process. Once the uptake is done, the technetium-99m accumulates in viable myocardial tissue delineating the infarcts areas when administered at rest and delineating the ischemic areas when administered at stress.
Toxicity
Technetium-99m tetrofosmin has a very high safety margin in both single and repeated dose intravenous administration. It does not exhibit mutagenic potential in vitro and in vivo. Reports have shown that technetium-99m tetrofosmin can cross the placenta thus, the possibility of pregnancy should be assessed.
Volume of Distribution
Reports have shown that it is possible to perform heart diagnosis and analysis as early as 5 minutes post-injection. After absorption, technetium-99m tetrofosmin is accumulated in the myocardium, skeletal muscle, liver, spleen and kidneys. If administered during exercise, there is a sequestration of technetium-99m tetrofosmin by skeletal muscle due to increased flow in skeletal tissue.
Elimination Route
After intravenous admministration, technetium 99m tetrofosmin is taken up in the heart where the uptake is done by potential-driven diffusion of the lipophilic cationic complex accross the sarcolemmal and mitochondrial membranes. The uptake in myocardium represents approximately 1.2% of the administered activity after 5 minutes of injection and this activity reduces to 1% at 2 hours. Once taken by the myocardium, there is a minimal redistribution in the following 3-4 hours.
Half Life
Technetium-99m tetrofosmin presents a very short half-life of 6.03 hours which is an advantage over other labeled radiopharmaceuticals.
Clearance
Technetium-99m tetrofosmin has a rapid clearance from the liver, lung and blood. The whole body clearance after 48 hours represents approximately 70% of the administered dose. Blood and plasma clearance follows an equal clearance profile in which at 10 min post injection there was less than 5% of the initial administered dose. The initial rate of urinary clearance accounts for 40% of the administered dose after 48 hours of the initial dose administration.
Elimination Route
The elimination of technetium-99m tetrofosmin is roughly the same for both fecal and urinary excretion and both account for apporximately 50% of the total excreted dose. The washout from the heart is slow and it depends on the patient state being of 4% per hour at exercise and 0.6% at rest. Complete elimination occurs after 48 hours. In this process, renal clearance accounts for approximately 40% of the administered dose in both rest and excercise; while fecal clearance accounts for 26-41% of the administered dose at rest and 17-34% of the administered dose after exercise.
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