In the mid-1970s, the racing industry launched a bold experiment designed to cure some of its most serious ills, and to help horses overcome some of theirs.

Politely called "controlled medication," it meant the abandonment of the historic prohibitions against giving drugs to racehorses. People in almost all segments of the racing industry embraced the belief that certain medications would benefit the sport.

In only a few years, controlled medication programs have become a scandal and an embarrassment across the country. In Maryland, as of today, the program is over. When Bowie Race Course opens its summer meeting this afternoon, horses will be fueled by hay and oats -- not Butazolidin and Lasix. The state racing commission finally issued its order banning the drugs last week, after public opinion against them had become so strong.

Only one segment of the racing community -- the horsemen -- is still trying to preserve controlled medication. Maryland trainers have been threatening boycotts and legal action, citing the hardships that the new restrictions will cause them.

But it was these same trainers whose abuses made controlled medication fail so miserably. They are fighting for a lost cause now, and nobody is listening to their arguments any more.

In 1973 and 1974, horsemen in Maryland and most other racing states had a very receptive audience when they made their pitch for legalizing bute, a painkiller and analgesic; and Lasix, which helped horses with the tendency to bleed through the nostrils.

The horsemen's argument seemed irrefutable. The sport had changed dramatically since the bygone days when there was a definable racing season. Now most states were conducting the sport year-round, and horses no longer had an offseason in which to recover from the inevitable wear and tear of racing. Medication would help the horses withstand the stress of year-round racing.

When the drugs were legalized, trainers did not employ them in anything resembling a judicious or "controlled" manner. Even casual race fans quickly grew suspicious about the use of Lasix.

The drug had been legalized for use on bleeders and no more than 5 percent of all thoroughbreds are potential bleeders. So why were 58 of the 81 horses entered on Pimlico's closing-day program racing with Lasix?

The most popular and plausible answer was that these legal drugs helped camoulfage the presence of illegal substances in a horse's urinalysis. Indeed, the era of controlled medication has seen the use of powerful illegal drugs like Sublimaze reach almost epidemic proportions.

Even though bute and Lasix were being overused, they did not accomplish what their proponents had said they would. The argument that drugs would help horses better withstand the rigors of year-round racing proved utterly false.

At the start of the decade, the average American thoroughbred raced 10.3 times a year.In 1974 the figure was the same. But since then it has dropped steadily, and last year the average horse went to the post only 9.6 times.

While controlled medication was not making any obvious positive contribution to the sport, it was creating a backlash. Expert veterinarians and chemists always described Ubtazolidin as useful, benign and mild - giving it to a horse was like giving aspirin to a human -- but the public never got the message.

When bute-treated horses broke down on the track, such as the one who killed jockey Robert Pineda at Pimlico, people increasinly blamed the fact that the animals had been "drugged." This reaction may have been a bit hysterical, but when CBS' "60 minutes" presented a one-sided report on the evils of drugs in racing, American public opinion was galvanized.

That sentiment took form in ridiculously heavy-handed bills introduced by Sen. David Pryor (D-Ark.) and Rep. Bruce Vento (D-Minn.) that could send a trainer to prison for giving a horse Butazolidin. Frightened by the possibility of federal intervention in the sport, racing officials were forced to find some answer to the drug problem. Last month the National Association of State Racing Commissioners unveilded a model medication programs, and it is that set of stringent guidelines which Maryland adopts today.

Bute is abused when it is giving to horses who shouldn't be running; but it is beneficial when it helps sore-legged horses get through their training. Racing officials would like to have specified that horses may take the drug except in the 24-hour period before they run.

Unfortunately, there would be no way to enforce such a standard. Instead, the new rules specify the amount of bute that may show up in a postrace blood test. The permissible limits are defined as two micrograms of bute per milliliter of plasma. The commissioners think this trace of bute would be present in the blood of a horse who has trained on the drug but hasn't had it for 24 hours.

Trainers and vets are going to have to experiment to discover how long before a race they can permissibly administer bute to a horse, and the Maryland Racing Commission has said that the rules will be leniently enforced at first.

But the guidelines may well turn out to be a lot tougher than even the commissioners and the horsemen think. Dr. Thomas Tobin, professor of pharmacology at the University of Kentucky, has been conducting research on the subject, and he said, "If you give bute to a horse 24 hours before a race, there is an 80 percent possibility that he will be over the limit. I would have to advise horsemen not to medicate in the three days before racing."

The new rules will drastically control the use of Lasix, too. It can now be given only to horses whom a state veterinarian has observed bleeding on the track at the conclusion of a race. Horses who are treated with Lasix may not be given the drug within five hours of post time, and they will be quarantined during this period.

Maryland horseman have protested that the Lasix rules are too strict, the bute rules too vague, and some have said that they will race their horses in other states if the commission makes these prohibitions stick.

Once such a threat might have been forceful; now it is hollow.As antidrug sentiment sweeps the country, there are not going to be many states left where trainers can use bute and Lasix with impunity. The new drug rules are ones that horsemen are going to have to live with for a long time.