A US prescription will have zero validity in Argentina. Some things that are available only with a prescription in the US (e.g. birth control bills, some antibiotics) are available in Argentina without a script.

The brand names will almost certainly be different, as might formulations and dosages, even for similar drugs.

I wouldn't chance getting what you need without going to an Argentine physician. It's not like going to Mexico, as some people do who live near the US border, and you can't assume that the pharmacy employees will speak English.

Besides which, if you have insurance in the US, there probably isn't going to be a cost savings by attempting to buy drugs here. Many Argentines have insurance plans which also give them a discount on drugs.

John