AMMONIA N 13
Clinical safety rating: caution
Comprehensive clinical and safety monograph for AMMONIA N 13 (AMMONIA N 13).
Ammonia N 13 is a radioactive diagnostic agent that is used as a tracer for positron emission tomography (PET) imaging. After intravenous injection, it distributes in the body and is taken up by cells, particularly in the myocardium and brain, via active transport and passive diffusion. Its accumulation reflects regional blood flow and metabolic activity.
| Metabolism | Ammonia N 13 is rapidly cleared from the blood and metabolized primarily to glutamine via the enzyme glutamine synthetase. A minor amount is converted to urea through the urea cycle. The radioactive tracer decays by positron emission with a half-life of 9.96 minutes. |
| Excretion | Primary renal excretion; >95% eliminated as unchanged ammonia via glomerular filtration and tubular secretion. Minimal biliary/fecal excretion. |
| Half-life | 9–12 minutes (blood) for ammonia; incorporation into glutamine may extend effective half-life for imaging purposes; rapid clearance limits toxicity. |
| Protein binding | <5% bound to plasma proteins (albumin); negligible binding. |
| Volume of Distribution | 0.3–0.5 L/kg, reflecting distribution into total body water and rapid equilibration with tissues. |
| Bioavailability | Not applicable for oral use; given IV only (100% bioavailability). |
| Onset of Action | IV: immediately upon injection for imaging; pharmacodynamic effect on pH balance occurs within seconds. |
| Duration of Action | Imaging signal diminishes rapidly with half-life; metabolic effects last minutes; used primarily for PET imaging with no long-lasting clinical effect. |
1110-1850 MBq (30-50 mCi) intravenous bolus for PET imaging; single dose per imaging session. No repeated dosing within 24 hours.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required. Renal impairment does not alter pharmacokinetics as the drug is eliminated primarily via decay and minimal renal excretion. |
| Liver impairment | No dose adjustment required. Hepatic impairment does not significantly affect distribution or clearance. |
| Pediatric use | 5.18 MBq/kg (0.14 mCi/kg) intravenous; minimum dose 74 MBq (2 mCi), maximum 370 MBq (10 mCi). Based on EANM pediatric dosage card. |
| Geriatric use | No specific dose adjustment; administer same adult dose (1110-1850 MBq). Age-related physiological changes do not necessitate modification due to short half-life (9.96 minutes) and tracer kinetics. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for AMMONIA N 13 (AMMONIA N 13).
| Breastfeeding | Not studied; expected to be excreted in breast milk. Due to short half-life, recommend interrupting breastfeeding for 2 hours after administration. M/P ratio unknown. |
| Teratogenic Risk | No human data; animal reproductive studies not conducted. Ammonia N-13 is a radioactive diagnostic agent with short half-life (10 min); theoretical risk from radiation exposure. Use only if benefit outweighs risk. First trimester: minimize exposure due to organogenesis; second/third trimester: low risk from diagnostic doses. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to ammonia or any component of the formulation"]
| Precautions | ["Radiation exposure: Use only in patients where the benefit outweighs the risk of radiation exposure.","Allergic reactions: Risk of hypersensitivity reactions including anaphylaxis.","Drug interactions: None known.","Pregnancy and lactation: Use only if clearly needed; consider risks to fetus and nursing infant."] |
| Food/Dietary | No food interactions are known for Ammonia N 13. However, patients should avoid caffeine and nicotine for 24 hours prior to the myocardial perfusion scan as they may interfere with test results. A low-carbohydrate, caffeine-free diet may be recommended for at least 12 hours before the procedure. |
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| Fetal Monitoring |
| Monitor for radiation exposure to fetus if used. Ensure justification per institutional guidelines for pregnant patients. No specific maternal monitoring required beyond standard for diagnostic procedure. |
| Fertility Effects | No known effects on fertility. Ammonia N-13 not studied for reproductive impact; theoretical risk from radiation, but diagnostic doses are unlikely to affect fertility. |
| Clinical Pearls | Ammonia N 13 is a radioactive diagnostic agent used for PET imaging of myocardial perfusion. It has a very short half-life (9.96 minutes) and must be prepared and administered promptly after production. Due to its rapid decay, imaging should begin immediately after injection. Ensure accurate timing of injection and scan acquisition. Renal function should be assessed as excretion is primarily renal. Use in pregnancy only if clearly needed; verify non-pregnancy status. Breastfeeding should be interrupted for at least 4 hours post-administration. Monitor injection site for extravasation, which can cause radiation exposure to local tissues. |
| Patient Advice | This is a radioactive drug used to evaluate blood flow to the heart muscle during a PET scan. · You will receive an injection into a vein, and imaging will begin shortly after. · The amount of radiation exposure is low and considered safe for diagnostic purposes. · Inform your doctor if you are pregnant or breastfeeding. · Drink plenty of fluids after the procedure to help eliminate the radioactive material from your body. · Avoid close contact with pregnant women and infants for several hours after the scan. |