Consider that when I fly out of Saudi Arabia, I always take a month’s worth of my medications. Some of them are controlled in the US, but not here in Saudi Arabia.
Heck, almost nothing in Saudi Arabia is on prescription. (Ritalin being the only exception I have ever run into.)
So I come through US Customs with:
Testosterone (a Class III drug)
A mess of blood pressure medications
Can Customs ask me for a prescription? What if I give him one in Arabic, would that work? Honestly, I have never heard of such a thing.