What is a CAS number and why are they important?
The Chemical Abstracts Service (CAS), a division of the American Chemical Society (ACS), assigns unique numerical identifiers, also known as Registry Numbers (RN), to chemical compounds. The Chemical Abstracts Service organizes and collects all publicly available chemistry information from numerous databases, scientific publications, and official regulatory agencies (i.e. FDA, EMA, etc.) to provide a thorough and complete collection of content linked to a unique CAS RN.
The CAS RN has become the international standard used by scientists, industry, and regulatory bodies worldwide as a reliable link between the variable nomenclature often used to describe the same compound.
The varied nomenclature of chemical compounds makes searching by compound name difficult and can lead to missing valuable information. The CAS Registry contains more than 142 million organic and inorganic compounds and 67 million sequences. Searching by CAS RN allows for a thorough search of the databases and scientific literature to ensure a more complete collection of available information for each compound. A CAS RN contains up to 10 digits and is divided into three parts by hyphens (i.e., XX-XX-X). These numbers designate an individual chemical substance and while they have no chemical significance, they serve as a unique identifier that allows anyone to find a desired compound with confidence.
It is important to note that the base and the various salt forms of a molecule will have different CAS RN; however, in the majority of cases, the OEL and ADE are the same for both the base and salt form. In addition, enantiomers of two stereoisomers will each have a unique CAS RN.
When requesting an OEL Fastrac monograph(s), in order to ensure a proper match, it is critical that we are provided with the CAS RN for each molecule. The CAS RN can typically be found on the Safety Data Sheet (SDS) or the Certificate of Analysis (CoA) that was provided for the active pharmaceutical ingredient (API) or the excipient. However, we have found that CAS RN presented on SDSs from API and excipient suppliers are often not valid numbers and should be carefully vetted by comparing those numbers with those found in one of the databases listed below.
For more information about CAS RN numbers, please visit the following websites: