is a terminology created and maintained by Veterans Health Administration in the United States. In 2018, it replaced NDF-RT that was used during 2005–2017. Med-RT is not included in RxNorm but is included in National Library of Medicine's UMLS Metathesaurus. Prior 2017, NDF-RT was included in RxNorm. The first release of MED-RT was in the spring of 2018. The United States Food and Drug Administration requires in its Manual of Policies and Procedures (MaPP) 7400.13 dated July 18, 2013 and updated on July 25, 2018, that MED-RT be used for selecting an established pharmacologic class (EPC) for the Highlights of Prescribing Information in drug labeling. Each EPC text phrase is associated with a term known as an EPC concept. EPC concepts use a standardized format derived from the U.S. Department of Veterans Affairs, Veterans Health Administration (VHA) Medication Reference Terminology (MED-RT). Each EPC concept also has a unique standardized alphanumeric identifier code, used as the machine-readable tag for the concept. These codes enable SPL indexing. The exact EPC text phrase used in INDICATIONS AND USAGE in Highlights might not be identical to the wording used to describe the EPC concept, because the standardized language used for the EPC concept might not be considered sufficiently clear to the readers of the labeling. Each active moiety also may be assigned MOA, PE, and CS standardized indexing concepts, which are also linked to unique standardized alphanumeric identifier codes. MOA, PE, and CS standardized indexing concepts may or may not be related to the therapeutic effect of the active moiety for a particular indication, but they should still be scientifically valid and clinically meaningful. Even if the MOA, PE, and CS standardized indexing concepts are not known with certainty to be related to the therapeutic effect, they may still be useful for identifying drug interactions and permitting other safety assessments for a moiety based upon appropriate and relevant considerations, such as enzyme inhibition and enzyme induction. MOA, PE, and CS concepts are maintained in a standardized format as part of the MED-RT hierarchy. https://www.fda.gov/media/86437/download The United States Food and Drug Administration Study Data Technical Conformance Guide dated July 2020 states, "6.5 Pharmacologic Class 6.5.1 Medication Reference Terminology 6.5.1.1 General Considerations The Veterans Administration's Medication Reference Terminology (MED-RT) should be used to identify the pharmacologic class(es) of all active investigational substances that are used in a study (either clinical or nonclinical). This information should be