Your doc in the US will provide what amounts to a written prescription. Remind her to include not only the branded name, but the generic compound as branded names vary by country and are of no consequence. The information on the written prescription should match the label on the container and the container should not include an excessive quantity, e.g. a 90-day supply for a 3-day visit.
The chances that you will need this are slim, but if you are asked, simply provide it and that will be the end of it.