A friend who spends a good deal of time here forgot to pack his locally-purchased meds when he returned to the US. He was continuing on to Europe a week later on a work assignment. He called his US doctor for prescriptions but found the doctor was on vacation for 2 weeks. So he called and asked me to send the left-behind meds via express mail.
I asked him to call DHL, which I find the most reliable courier between here and the US, and confirm that there were no restrictions. He called back and said the agents there told him there shouldn't be any problem if the parcel were marked "personal items."
So I went to DHL, which insisted I use their packaging. But when the agent saw the contents, she wouldn't accept them. Said the US authorities don't let them through. So I tried the Correo, with the same results. Calls to UPS and Fedex here got the same results, although when my friend called their US offices, he was told the same story he had heard from DHL.
With these complications, he ended up getting another doctor to write the prescriptions, which he bought at US prices, and then followed up in Europe, where prices are much better than in the US.
Based on what the US agents said, I suspect if you can find a way to get a parcel accepted here with your packaging, it may get delivered in the US without problems. But that's still a "maybe," and both the DHL and Correo agents I saw wanted to inspect the contents before they would accept them.
