Kentucky Derby winner Medina Spirit walks around the Stakes Barn with assistant trainer Jimmy Barnes after arriving at Pimlico Race Course Monday.

BALTIMORE — Medina Spirit has passed his three drug tests this week and will be running Saturday in the Preakness Stakes. Word came Friday afternoon that the Kentucky Derby winner, along with three other Bob Baffert horses are eligible to run.

As a condition of running, Baffert agreed to have all four of his horses tested before running at Pimlico Race Course this weekend after betamethasone, an anti-inflammatory, was discovered in Medina Spirit’s system. Stablemates Concert Tour, is the second-favorite in the Preakness, and Beautiful Gift is scheduled to run in Friday’s featured Black Eyed Susan Stakes for 3-year-old fillies. A fourth horse, Hozier, was tested only two times and will run in the Sir Barton Stakes on Saturday.

Maryland, as with Kentucky, California and most states, has a zero-tolerance policy for the drug on race day. It is a legal medication, usually used to treat joint inflammation and subsequent pain, but a horse has to be off it for at least 14 days before it can race. It is not considered a performance enhancer, according to two nationally known equine veterinarians contacted by The Los Angeles Times.

Medina Spirit was treated with an ointment that contained betamethasone for dermatitis on his hind quarter from shortly after the Santa Anita Derby to the day before the Kentucky Derby, or for about a month.

The banning of use of the medication prior to racing is so veterinarians can better detect any soundness problems with a horse. The drug decreases the inflammation, meaning that hot areas cannot be as easily detected in pre-race veterinary examinations.