Ammonia N 13 by is a Prescription medication manufactured, distributed, or labeled by University of Wisconsin System, UW Radiopharmaceutical Production Facility. Drug facts, warnings, and ingredients follow.
Ammonia N 13 Injection is a radioactive diagnostic agent for Positron Emission Tomography (PET) indicated for diagnostic PET imaging of the myocardium under rest or pharmacologic stress conditions to evaluate myocardial perfusion in patients with suspected or existing coronary artery disease (1).
Rest Imaging Study (2.1):
Stress Imaging Study (2.2):
Patient Preparation (2.3):
Glass vial containing 0.138-1.387 GBq (3.75-37.5 mCi/mL) of Ammonia N 13 Injection in aqueous 0.9 % sodium chloride solution (approximately 8 mL volume) (3).
Ammonia N 13 Injection may increase the risk of cancer. Use the smallest dose necessary for imaging and ensure safe handling to protect the patient and health care worker (5).
No adverse reactions have been reported for Ammonia N 13 Injection based on a review of the published literature, publicly available reference sources, and adverse drug reaction reporting system ( 6).
To report SUSPECTED ADVERSE REACTIONS, contact University of Wisconsin Radiopharmaceutical Production Facility at (608) 263-0359 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. (6)
See 17 for PATIENT COUNSELING INFORMATION.
To increase renal clearance of radioactivity and to minimize radiation dose to the bladder, ensure that the patient is well hydrated before the procedure and encourage voiding as soon as a study is completed and as often as possible thereafter for at least one hour.
The converted radiation absorbed doses in rem/mCi are shown in Table 1. These estimates are calculated from the Task Group of Committee 2 of the International Commission on Radiation Protection.1
|Organ||Adult||15 - year old||10 - year old||5 - year old||1 - year old|
*Upper large intestine, **Lower large intestine
Pregnancy Category C
Animal reproduction studies have not been conducted with Ammonia N 13 Injection. It is also not known whether Ammonia N 13 Injection can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Ammonia N 13 Injection should be given to a pregnant woman only if clearly needed.
It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk and because of the potential for radiation exposure to nursing infants from Ammonia N 13 Injection, use alternative infant nutrition sources (e.g. stored breast milk or infant formula) for 2 hours (>10 half-lives of radioactive decay for N 13 isotope) after administration of the drug or avoid use of the drug, taking into account the importance of the drug to the mother.
Ammonia N 13 Injection 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, and has the following chemical structure:
Ammonia N 13 Injection is provided as a ready to use sterile, pyrogen-free, clear and colorless solution. Each mL of the solution contains between 0.138 GBq to 1.387 GBq (3.75 mCi to 37.5 mCi) of [13N] ammonia, at the end of synthesis (EOS) reference time, in 0.9% aqueous sodium chloride. The pH of the solution is between 4.5 to 7.5.The recommended dose of radioactivity (10-20 mCi) is associated with a theoretical mass dose of 0.5-1 picomoles (8.47-16.94 picograms) of ammonia.
Nitrogen N13 decays by emitting positron to Carbon C13 (stable) and has a physical half-life of 9.96 minutes. The principal photons useful for imaging are the dual 511 keV gamma photons that are produced and emitted simultaneously in opposite direction when the positron interacts with an electron (Table 2).
|Radiation/Emission||% Per Disintegration||Energy|
|Positron(β+)||100||1190 keV (Max.)|
*Produced by positron annihilation
The specific gamma ray constant (point source air kerma coefficient) for nitrogen N13 is 5.9 R/hr/mCi (1.39 x 10-6 Gy/hr/kBq) at 1 cm. The half-value layer (HVL) of lead (Pb) for 511 keV photons is 4 mm. Selected coefficients of attenuation are listed in Table 3 as a function of lead shield thickness. For example, the use of 39 mm thickness of lead will attenuate the external radiation by a factor of about 1000.
|Shield Thickness (Pb) mm||Coefficient of Attenuation|
Table 4 lists fractions remaining at selected time intervals from the calibration time. This information may be used to correct for physical decay of the radionuclide.
Ammonia N 13 Injection is a radiolabeled analog of ammonia that is distributed to all organs of the body after intravenous administration. It is extracted from the blood in the coronary capillaries into the myocardial cells where it is metabolized to glutamine N 13 and retained in the cells. The presence of ammonia N 13 and glutamine N 13 in the myocardium allows for PET imaging of the myocardium.
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.
Following intravenous injection, Ammonia N 13
Injection is cleared from the blood with a biologic half-life of
about 2.84 minutes (effective half-life of about 2.21 minutes). In the myocardium, its biologic half-life has
been estimated to be less than 2 minutes (effective half-life less than 1.67
The mass dose of Ammonia N 13 Injection is very
small as compared to the normal range of ammonia in the blood
(0.72-3.30 mg) in a healthy adult man [see Description (11.1)].
Plasma protein binding of ammonia N 13 or its N
13 metabolites has not been
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.
Ammonia N 13 is eliminated from the body by
urinary excretion mainly as urea
The pharmacokinetics of Ammonia N 13 Injection have not been studied in renally impaired, hepatically impaired, or pediatric patients.
In a descriptive, prospective, blinded image interpretation study2 of adult patients with known or suspected coronary artery disease, myocardial perfusion deficits in stress and rest PET images obtained with Ammonia N 13 (N=111) or Rubidium 82 (N=82) were compared to changes in stenosis flow reserve (SFR) as determined by coronary angiography. The principal outcome of the study was the evaluation of PET defect severity relative to SFR.
PET perfusion defects at rest and stress for seven
apical, anteroseptal, posteroseptal, anterolateral, posterolateral, and
inferior walls) were graded on a 0 to 5 scale defined as normal (0), possible
(1), probable (2), mild (3), moderate (4), and severe (5) defects. Coronary
angiograms were used to measure absolute and relative stenosis dimensions and
to calculate stenosis flow reserve defined as the maximum value of flow at
maximum coronary vasodilatation relative to rest flow under standardized
hemodynamic conditions. SFR scores
ranged from 0 (total occlusion) to 5 (normal).
With increasing impairment of flow reserve, the subjective PET defect severity increased. A PET defect score of 2 or higher was positively correlated with flow reserve impairment (SFR<3).
Ammonia N 13 Injection is packaged in 10 mL mulitiple dose glass vial containing between 1.11 GBq to 11.1 GBq (30 mCi to 300 mCi) of [13N] ammonia, at the end of synthesis (EOS) reference time, in 0.9% sodium chloride injection solution in approximately 8 mL volume. The recommended dose of radioactivity (10-20 mCi) is associated with a theoretical mass dose of 0.5-1 picomoles (8.47-16.94 picograms) of Ammonia.
Store at 25°C (77°F); excursions permitted to 15-30°C (59-86°F).Use the solution within 35 minutes of the End of Synthesis (EOS) calibration.
Instruct patients to drink plenty of water or other fluids (as tolerated) in the 4 hours before their PET study.
Instruct patients to void after completion of each image acquisition session and as often as possible for one hour after the PET scan ends.
|AMMONIA N 13
ammonia n 13 injection
|Labeler - University of Wisconsin System (161202122)|
|Registrant - University of Wisconsin System (161202122)|
|UW Radiopharmaceutical Production Facility||117218915||positron emission tomography drug production(72333-001)|