It has been about 3 years since I have done that. They did require that you show a Dr's prescription for them for a while, I do not know now. But you can probably get that in Mexico too. Algodones by Yuma has a huge amount of people crossing the border to buy meds, glasses and get dental work done, some of the dentists are very good. There are 900 dentists and at least 25 pharmacies in about a 8 block area. Here are some rules for buying meds.
I bought Ivermectin and Hydroxycloriquine from India, no script, nothing. It got here in a week.
For more information dial: 1-800-CARTEL
They'll get you anything you want.