Q: Must a medical practice create a list of all hazardous substances used in the workplace? It seems as if the MSDS file already covers that information.
A: Yes, the Hazard Communication standard  does require the employer to compile a list of hazardous substances in the workplace as part of the written plan:
1910.1200(e)(1)(i) A list of the hazardous chemicals known to be present using an identity that is referenced on the appropriate material safety data sheet (the list may be compiled for the workplace as a whole or for individual work areas)…
You can save some time by just referencing the name of the chemical as it appears on the MSDS and indicating you have the MSDS on file. While the other information is good to have, OSHA does not require it as long as you have the MSDS.