Answer :
Mary was told to see a different doctor at Lockwood Medical Center since her regular doctor, Dr. Acula, was on vacation.
You must capitalize Lockwood Medical Center that is a Name of a place a proper noun
doctor is a common noun in both places you do not capitalize a common noun
Dr. Acula Must both be capitalized it is a proper noun the doctor's title and name
Mary was told to see a different doctor at Lockwood Medical Center since her regular doctor, Dr.Acula, was on vacation.