But Luca Cumani, an Italian trainer now based in Britain, is unconvinced that snake venom could be effective.
"It's something that's been around for years, but there are much more sophisticated drugs that have been applied to horses," he said.
Roy and Gretchen Jackson, Barbaro's owners, are based in West Grove, Pa. They are above suspicion of any such drug use, say U.S. horse-racing experts, but other high-flying trainers have recently run afoul of racing authorities.
Todd Pletcher, whose horses took in about $30 million in 2006, became the most successful U.S. trainer that year. However, he was given a 45-day suspension in December, after one of his horses tested positive for an anesthetic drug while racing at Saratoga in August 2004.
The New York State Racing and Wagering Board still imposed the suspension despite two major appeals.
The lines between legitimate medication and illegal drug use in American racehorses are further blurred by conflicting state laws.
Italian trainer Cumani says that the distinction in U.S. racing is itself complicated. "It is a very emotional word, since all these medications are lumped into the term 'drugs.' You say that a horse is on drugs, and it immediately conjures up all sorts of things. Right now, the authorities are not up to tackling the difference between drugs and medication," he said.
Phenylbutazone, commonly known as "bute," is another drug that can be misused by American trainers.
However, Waterman said he believed the use of painkillers on horses slated to race on a given day was now very unusual.
But Brian Meehan, a British trainer whose horses have scored notable successes at the Kentucky Derby in recent years, does not believe there is any problem with the American drug allowances in racing.
"Once you know the limits and the regulations, there should be no problems," he said.