# Ammonia N-13

Source: https://nuclide.cc/drugs/n-13-ammonia/  
Nuclide record `n-13-ammonia` (Agent). Data CC BY-NC 4.0, attribute "Data from Nuclide (nuclide.cc)"; commercial use needs a licence.

## TL;DR

A radioactive form of ammonia gas, made fresh on site in a cyclotron and injected into a vein; heart muscle cells trap it in proportion to how much blood is flowing through, so a PET scan maps blood flow to the heart very precisely.

## Summary

Ammonia N-13 injection is a cyclotron-produced PET myocardial perfusion agent, initial US approval 2007 (NDA 22-119, full approval 2011), taken up and metabolically trapped in myocytes as N-13 glutamine, giving image quality and quantitative accuracy that ASNC/SNMMI guidelines rate among the best of the FDA-approved and CMS-reimbursable PET perfusion tracers (the others being Rb-82; O-15 water is used in Europe but is not FDA approved).

The FDA label indicates it for diagnostic PET imaging of the myocardium under rest or pharmacologic stress to evaluate myocardial perfusion in patients with suspected or existing coronary artery disease. The recommended adult dose is 10-20 mCi (0.368-0.736 GBq) as an intravenous bolus for each of the rest and stress studies, with the stress study begun 40 minutes or more after the first injection to allow adequate decay of the 9.97-minute isotope; imaging starts about 3 minutes after injection.

Because it requires an on-site or very nearby cyclotron (unlike generator-based Rb-82), N-13 ammonia's use is concentrated at academic and large hospital PET centres; it is the other guideline-endorsed option, alongside Rb-82, for the resting perfusion half of the two-part cardiac sarcoidosis PET protocol, and is favoured by some centres for absolute myocardial blood flow quantification given its longer half-life relative to Rb-82, which allows more complete kinetic sampling.

## Fields

- Kind: Agent
- Last checked: 2026-09-22
- Also known as: 13N-ammonia; N-13 ammonia
- Tags: PET; myocardial perfusion; cyclotron
- Modality: PET tracer
- Mechanism: N-13 ammonia (as NH3/NH4+) diffuses into myocytes and is metabolically trapped as N-13 glutamine by glutamine synthetase, giving high myocardial uptake proportional to blood flow. Its 9.97-minute physical half-life requires an on-site cyclotron, in contrast to generator-produced Rb-82, but permits standard two- or three-compartment kinetic modelling for absolute myocardial blood flow quantification (mL/min/g) using dynamic PET acquisition.
- Approvals: US 2007: Diagnostic PET imaging of the myocardium under rest or pharmacologic stress to evaluate myocardial perfusion in patients with suspected or existing coronary artery disease
- Dosing: Intravenous bolus injection; 10-20 mCi (0.368-0.736 GBq) per rest or stress study; imaging begins about 3 minutes after injection for 10-20 minutes; stress study begun 40+ minutes after the rest dose

## Sources

- FDA label: Ammonia N 13 Injection, 2011 revision: https://www.accessdata.fda.gov/drugsatfda_docs/label/2011/022119s001lbl.pdf
- FDA approval package, NDA 22-119/S-001: https://www.accessdata.fda.gov/drugsatfda_docs/nda/2011/022119orig1s001.pdf
- ASNC/SNMMI PET nuclear cardiology procedure standard: https://www.asnc.org/wp-content/uploads/2024/06/s12350-016-0522-3.pdf

## Connected records

- drugs: [Flurpiridaz F-18](https://nuclide.cc/drugs/f-18-flurpiridaz/), [Rubidium Rb-82 chloride](https://nuclide.cc/drugs/rb-82-chloride/)
- isotopes: [Nitrogen-13](https://nuclide.cc/isotopes/n-13/), [Oxygen-15](https://nuclide.cc/isotopes/o-15/), [Rubidium-82](https://nuclide.cc/isotopes/rb-82/)
- indications: [Cardiac sarcoidosis](https://nuclide.cc/indications/cardiac-sarcoidosis/), [Coronary artery disease](https://nuclide.cc/indications/coronary-artery-disease/)

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