Unii-9oqo0E343z

Absorption

Following intravenous injection, 13N-ammonia is cleared rapidly from the blood with a biologic half-life of about 2.84 minutes (effective half-life of about 2.2 minutes). In the myocardium, its biologic half-life has been estimated to be less than 2 minutes (effective half-life less than 1.67 minutes).

Toxicity

Data not available.

The Uses of Unii-9oqo0E343z

Diagnostic aid (cardiac imaging); diagnostic aid (liver imaging); radioactive agent.

Indications

For diagnostic Positron Emission Tomography (PET) imaging of the myocardium under rest or pharmacologic stress conditions to evaluate myocardial perfusion in patients with suspected or existing coronary artery disease.

Background

Ammonia N 13 Injection, USP is a positron emitting radiopharmaceutical that is used for diagnostic purposes in conjunction with positron emission tomography (PET) imaging. The active ingredient, [13N] ammonia, has the molecular formula of 13NH3 with a molecular weight of 16.02. Ammonia N 13 Injection, USP is used for imaging of the myocardium under rest or pharmacologic stress conditions to evaluate myocardial perfusion in patients with suspected or existing coronary artery disease.

Definition

ChEBI: Ammonia-(13)N is a (13)N-modified compound that is ammonia that has a (13)N isotope as the nitrogen atom. (13)N decays with a half-life of ten minutes to (13)C, emitting a positron. Used in diagnostic Positron Emission Tomography (PET) imaging. It has a role as a radioactive imaging agent.

Pharmacokinetics

Following intravenous injection, ammonia N 13 enters the myocardium through the coronary arteries. The PET technique measures myocardial blood flow based on the assumption of a three-compartmental disposition of intravenous ammonia N 13 in the myocardium. In this model, the value of the rate constant, which represents the delivery of blood to myocardium, and the fraction of ammonia N 13 extracted into the myocardial cells, is a measure of myocardial blood flow. Optimal PET imaging of the myocardium is generally achieved between 10 to 20 minutes after administration.

Metabolism

Ammonia N 13 undergoes a five-enzyme step metabolism in the liver to yield urea N 13 (the main circulating metabolite). It is also metabolized to glutamine N 13 (the main metabolite in tissues) by glutamine synthesis in the skeletal muscles, liver, brain, myocardium, and other organs. Other metabolites of ammonia N 13 include small amounts of N 13 amino acid anions (acidic amino acids) in the forms of glutamate N 13 or aspartate N 13.