Average sized, it's owned by Renesco under the protection of the Salvatores. He employs several New Reno citizens and junkies to manufacture his drugs and chems and store them. However, as the man is short sighted, the place is less than orderly, to the point of something resembling brahmin crap littering the shelves, possibly due to Renesco's inability to see what his store looks like with his broken glasses. C'est la vie.
Renesco's Pharmacy appears only in Fallout 2.