Horse racing took a significant step toward adopting tough uniform rules nationwide Tuesday when eight states agreed to operate their racetracks under one set of rules that will severely restrict the administration of medication.

The states across the Mid-Atlantic region, including New York, winnowed what has long been an unruly list of medications to just 24 that will be allowed to treat illness and injury in racehorses. Those will be subject to strict limitations and the laboratories conducting drug tests must be accredited under standards created by the Racing Medication and Testing Consortium, which conducts medication and drug-testing research for the industry.

“We want state of the art labs testing the same way for the same things,” said Alan M. Foreman, the chairman of the Thoroughbred Horsemen’s Association. “You can’t find any other sport that allows just 24 drugs. We’ve been in the cross hairs, for good reason, and this is an initiative that no horsemen’s group — or anyone else — can find a reason not to get behind. It will do good things for the safety and welfare of the horse and the riders.”

This latest push comes as racing has publicly wrestled with a drug culture that its officials concede is diminishing the sport. Congressional hearings have been held, and federal legislation proposed to take over the sport.