U.S.P. 800 stands for United States Pharmacopeia, which is like a big book of rules that says how medicines and other drugs should be handled. All medicine that is used in U.S. hospitals and pharmacies must follow these rules, which are put in place to keep people safe. This means that all medicines and drugs must be stored in specific places, handled by people with special training, and checked very carefully before they are used. This helps make sure that the medicines and drugs are always safe for people to use.