Is it correct to say "I buy aspirin in/at the drugstore"?

Question

In some countries, a drugstore is like a small house with a window or big door and you just stand on the street or pavement in front of the window/door to buy. Only staff is allowed to go into that drugstore. In this case, it looks like a counter which sells medicine. See the picture below.

However, there are some bigger drugstores. You can go into the stores. The stores also sell other things such as umbrellas, tissues, sunglasses etc. You can go to a counter in the store to buy medicine. See the picture below.

Oxford dictionary has this example "I bought these sunglasses at the drugstore."

From Longman Dictionary has this example "For a number of years, artificial sweeteners were mainly used by diabetics, who bought the products in drugstores."

Is it correct to say "I buy aspirin in/at the drugstore"?

Note: some people prefer to say "I bought it from the drugstore"

Answer 1

All three of, "I bought it at/in/from the drugstore" are correct if you went inside the building. If you stayed outside, like the top picture above, then only "I bought it at/from the drugstore" are correct.

Generally, the difference between "in" and "at" is "in" requires the action to happen inside the building, while "at" means it happened in the area that's considered the place. If you're outside the drugstore at the window, this is still considered part of the drugstore itself, so "at" is still correct. If you're "at a school", you might be inside the building, or in the yard, or parked nearby.

To buy something "from" a place only means who you paid for the product, not where you were. I can buy medicine from drugstores from home, either by phone or over the Internet.