In an interview from the infield of Lowe's Motor Speedway on Saturday night, the Sprint Cup driver said he hasn't been told what he tested positive for, leading to his suspension a week ago.
Mayfield said he took the legal prescription drug Claritin D to treat allergies.
"A legal prescription drug, that's what I take," Mayfield said. "I had allergies at Richmond that were really, really bad. On (May 7) I got a call and said you've tested positive for whatever they called it.
I said, 'OK, no problem. I've got all my paperwork ready.' He said you'll fax that to us it'll cancel out your test."
But Mayfield said he didn't hear anything again until he was suspended indefinitely two days later.
ON THE MONEY: Stock car racing continued to separate itself from other professional sports Saturday night with its all-star race.
Not only was the Sprint All-Star race offer the most money a mile during the season, it attracted every full-time driver and most of the part-timers to the Lowe's Motor Speedway.
Race winners competed in the all-star race; others ran in the Sprint Showdown -- all with the goal of winning more than $1 million.
"Ours, there is a million dollars on the line and other all-star games I don't think they get that kind of money," Dale Earnhardt Jr. said. "I don't know what the deal is with the other all-star games. I don't know whether they get paid or not."
CHANGES IN THE AIR: Race fans have noticed, both in sluggish attendance and soft television ratings: the new Car of Tomorrow isn't very racy on the 1.5- and 2-mile tracks.
Some teams were told NASCAR is working on some changes on the car to promote more passing, especially at tracks like the Lowe's Motor Speedway. Teams may get those changes in the next couple weeks.
Since the new car was mandated for full-time use in 2008, most races on the intermediate tracks have runaway winners with very little passing in the lead pack.
BURNING DOWN THE HOUSE: Kevin Harvick turned a reputation for being a master of burnouts into a $10,000 payday Saturday when he won a burnout competition.
Six judges -- former racer Jimmy Spencer , singers Eddie Montgomery and Troy Gentry , actor Kevin Costner , retired wrestler Ric Flair and New England Patriots wide receiver Randy Moss -- gave Harvick 58 of a possible 60 points for a long burnout at the finish line.
Harvick stayed in one spot for 15 seconds with his tires smoking and squealing, twice sticking his hand out the window to encourage fans to cheer.