Supplementary Concept Records (SCRs) are used to index chemicals, drugs, and other concepts such as rare diseases for MEDLINE. New Supplementary Concepts can be added daily to the MeSH terminology, and therefore provide a way to accommodate new concepts for indexing, quickly. You can use Supplementary Concepts for searching and you will see your search terms mapped to SCRs whenever appropriate.

For example, try searching salvin in PubMed and check your Search Details:

If you see mapping to either a MeSH Term or Supplementary Concept in your Details, your concept has been found and you can feel confident that the relevant MEDLINE records will be retrieved.

SCRs are usually very specific, so limiting your search to the MeSH part of the MEDLINE record is usually not necessary. However, you can search SCRs included in the MeSH indexing by using the [NM] tag. For example, our previous PubMed search would be: salvin[nm].