Smarty Jones won the first six races of his career before trainer John Servis gave the colt a shot of Lasix -- or furosemide -- at the Kentucky Derby. The drug, classified as a diuretic, is used to treat hypertension and high blood pressure in humans and respiratory bleeding in horses. Smarty Jones never had shown signs of bleeding problems in the past, but Servis wanted to give the horse every chance to win the big race.

"I'd like to run him in the Derby without Lasix," Servis said in the days before running at Churchill Downs. "But I'd be heartbroken not only for myself but for [the owners] if I felt this horse could have won the Derby and he bled and got beat because of it. I'm trying to eliminate all the excuses."

Since New York in 1995 became the last racing state in the country to permit the use of Lasix before a race, five horses preceded Smarty Jones into the Belmont Stakes having won the Kentucky Derby and Preakness. None came away with the Triple Crown.

Trainer Ken McPeek, who won the Belmont in 2002 with 70-1 long shot Sarava, said this week that he believes one of the reasons might be because the 3-year-old colts are running three demanding, long-distance races in a seven-week span while trying to adjust to the debilitating properties of Lasix.

The drug not only stimulates the kidneys to produce more urine but also increases the excretion of sodium, chloride, potassium and water.

Studies have shown Lasix can improve a horse's performance, but over time, McPeek said, it can hurt as well.

"There is a misconception that it gives you an advantage," said McPeek, who doesn't have a horse entered in this year's Belmont. "I think Lasix dehydrates the horses. You look back at the horses that won the Triple Crown, and none have ever won with Lasix. It takes all the potassium and fluids out of your body. Can you put fluids back into a horse after a hard race? Of course you can. But after a while, it drains the horse."

McPeek, who, despite his concerns, regularly races his horses on Lasix, said Smarty Jones might have a distinct advantage in the Belmont Stakes because he ran as a 2-year-old without the drug and only just recently began to use it.

"Smarty might be [in a good position to win] because he hasn't been dehydrated through the winter," McPeek said.

In contrast, all the other runners being pointed toward the Belmont Stakes have raced on Lasix virtually their entire careers.

While Maureen Donnelly, Servis's assistant trainer, said she agreed with McPeek, others in racing did not.

"I completely disagree," said Nick Miettinis, track veterinarian at Pimlico, who has treated six of the past seven Preakness winners. "We can give them fluids to combat [dehydration]. We give them electrolytes every day for 12 months a year. Every horse that came off the airplane [for the Preakness] from New York and California, they got three to six liters of IV fluids within two or three hours of getting into Maryland. These horses are pampered."

Servis gave Smarty Jones four cubic centimeters of Lasix before the Derby and had Miettinis administer the same dose before the Preakness.

"Some people around Philadelphia Park give [horses] up to 10 cc's, and when they run only two weeks apart you can see dryness on their skin," Donnelly said.

Servis, according to his assistant, only gives young horses Lasix if they bleed, while also spacing out the races of all his runners to give them time to recover.

"Lasix has a tendency to take the edge off a horse," Donnelly said. "It does drain them to an extent."

After the Derby, Servis proceeded with caution before committing Smarty Jones to a run in the Preakness. Normally, he would never run a horse back in two weeks off such a demanding performance. Smarty Jones, however, came out of Kentucky in fine shape.

Horseplayers know it is often wise to bet on a horse receiving Lasix for the first time, but even better the second.

"A lot of people focus on first dope," said Bob Fornoff, a regular horseplayer from Baltimore, "but [some believe] that horses are a little confused the first time."

Miettinis supports this theory.

"[Lasix] helps horses regain the level of ability they may have had had they not bled," the vet said. "Horses that have been bleeding without detection, they use Lasix the first time and expect to still bleed. And they gallop out and see that they haven't. The next time they run, they're not worrying about it. Horses are creatures of habit."

Servis said Smarty Jones bled slightly after the Kentucky Derby -- "nothing to get excited about." In his second run on Lasix, the horse won the Preakness by 11 1/2 lengths, the widest margin of victory in the history of the race.

A study of the race records of 22,589 thoroughbreds conducted in 1999 at Ohio State University found 74 percent of them were likely to be running on Lasix. The study found horses were 1.4 times more likely to win than horses running without the drug.

With his imposing, undefeated record and proven ability to win with or without Lasix, Smarty Jones would be an overwhelming favorite in the Belmont on or off the drug.

"This horse, Smarty Jones, he's the real deal," Miettinis said.

Only Lion Heart, second in the Derby and fourth in the Preakness, raced in the Triple Crown this year without Lasix.

"I did not consider Lasix," Lion Heart's trainer Patrick Biancone said before the Preakness. "If I have a headache, I take aspirin. If I don't have a headache, I don't take aspirin."