In purchasing drugs and supplements, I've noticed that certain products are advertised as Pharmaceutical Grade. Wanting to know what qualifies a substance as pharmaceutical grade I did some googling and found the USP, which apparently sets drug purity standards for the FDA. But in visiting the USP website I find a USP dictionary will set me back $378.00. And the Reference Standards seems to be a comprehensive list of drugs, but instead of providing any useful info, each one is listed as a product that I can purchase for several hundred dollars.
openFDA label database doesn't seem to include any information on purity standards, just standard doses and dosages.
I'm incredulous that the definition of Pharmaceutical Grade for any given substance adopted by the FDA should be a secret I have to pay nearly $400 to learn. So my question is, is there some source I'm missing, either within, or outside openFDA?