One time my mom got a scrip order from the Dr., 2 hours later Walmart calls, explaining that the new scrip conflicts and has interactions with another of my moms regular scrips. Called the Doc about it and he talked with the PharmD. Got everything taken care of.
My mom is very allergic to certain meds and this would have been bad, if not caught by the PharmD.
If it isn’t fairly routine, the local Wal-mart grocery store isn’t going to have it in stock - it will be filled at a central dispensary and shipped to the store pre-packed. Call ahead a day or so for re-fills and they are great. A high power painkiller in an emergency, you might need to go elsewhere.
Wal-mart was also really good when I needed a re-fill a couple of states away. A couple of clicks on the computer and I was walking out with it in about 15 minutes.