MD pharmacologists do exist. 95% of my pharmacology courses at Iowa were taught by MD/PhDs who ran pharmacology labs and taught pharmacology courses. There pharmacology is a subdepartment of the College of Medicine. In no way were these faculty generalized medication experts. If anything their focus was more narrow than other physicians and they could probably not tell you the generic name for Prilosec.
A PhD in pharmacology isn't sufficient to practice pharmacy in the US. Pharmacy is a related discipline that includes study of multiple pharmaceutical sciences (pharmacology, pharmaceutics, medicinal chemistry, pharmacy practice) and concentrates more on training and delivering practitioners.
We just go to school for different things. A physician could do some parts of a pharmacist's job just fine. I just don't know that they would want to spend their time doing it. And, I don't know anyone who would want to pay you to do it.