Across/Across from

No...those create different meanings. A across from the pharmacy means that it is separate and outside the pharmacy...like another store or place. The grocery store is across from the pharmacy.

It's across the pharmacy isn't really natural...I mean you could say I walked across the pharmacy to get some deodorant...but it isn't natural. You would say things like...

I walked across the street to get to the bar.
I walked across the bridge with my eyes closed.

Does that makes sense?

"across the ..." means on the other side of ... or the path to the object

"It's across the street."
- means it's on the other side of the street.

Here the reference point is understood from the context or possibly the point of the speech act.

"across from ..." means opposite ...

"It's across from the supermarket."
- means 'it' and the supermarket sit directly opposite each other with the street between them

Here the reference point is the supermarket.

While they can both be used in some situations (but not interchangeably), the pharmacy example is pretty good to show the difference. with 'across the ...' you can have a much larger area between the reference point and the end point.

"He ran across the country."

Sorry, I'm rushed. I hope that makes sense.

Thank to both of you!

I'm glad it helps.