Q: Please state the regulation allowing the removal of a chemical/medication from it’s original container and placing it into another “unmarked” container for a “small” amount of time and then using it. What defines a “small” amount of time?
A: First of all the OSHA regulation you allude to is only for hazardous chemicals. I know of none for unlabeled medications, as would be expected.
Section 1910.1200(f)(7) of the Hazard Communication standard  addresses label requirements for transferring hazardous substance into secondary containers.
As I explain in an earlier post, “Ask the expert: Hazardous substances in unmarked containers,”  OSHA defines immediate use as:
The time during which the hazardous chemical is under the control of and in use only by the person transferring it from a labeled container and only within the work shift in which it is transferred.