Phoenix Racing called Allmendinger on Thursday and asked him to report immediately to Charlotte Motor Speedway to drive the No. 51 Chevrolet.
Regan Smith had been tabbed to drive the car, but is instead going to replace Dale Earnhardt Jr., who will miss the next two races with a concussion. Kurt Busch left the team this week for Furniture Row Racing.
Allmendinger was suspended after failing a random test for what, according to the driver, turned out to be Adderall, a prescription drug typically used to treat attention deficit disorder. He was reinstated by NASCAR last month and is looking for a job for 2013 after being dropped by Penske Racing three months ago.