The Maryland Racing Commission voted unanimously today to prohibit the use of any drugs at the state's thoroughbred tracks, effective Jan. 1.

The ban will affect two medications which are now legal, the painkiller Butazolidin and the diuretic Lasix. But testimony at the four-hour hearing suggested that some horsemen might respond by using other drugs which are more powerful, more dangerous and undetectable.

Maryland's action had been expected, since the commission last week announced that it was joining its counterparts in Pennsylvania, West Virginia and Delaware to establish uniform programs banning medication. Faced with such a prospect, which they consider a serious economic blow, horsemen came to the commission with a plan that would sharply limit the drugs' use.

Fendall Clagett, president of the area Horsemen's Benevolent and Protective Association, suggested the compromise: Horses could not be given Bute within 18 hours of a race. Lasix would be administered four hours beforehand, in a state-operated detention barn. These restrictions would eliminate the worst abuses of the drugs.

But these concessions by the horsemen came too late. The commissioners had made up their minds, and no amount of argument was going to change that.

Just a year ago, the same commission had listened to the same arguments and had upheld the use of Bute and Lasix. What had changed in the interim was not the drugs, but public opinion. Spurred largely by a report on drugs by CBS' "60 Minutes," many state legislatures are moving to pass laws prohibiting the use of medications. Racing commissions are trying to save face by beating them to it.

The pendulum has swung so completely that Maryland will not even permit the use of Lasix in the situation where it is most beneficial, to treat known "bleeders," horses who tend to bleed profusely from the nostrils during a race.

Horsemen felt that the commission, like the public and the politicians, were misapprehending the nature of the durgs they were opposing. "The big problem," said trainer King T. Leatherbury, "is that everybody is throwing in two simple, safe drugs with a whote batch of illegal drugs. Abolishing medication may sound good but it's naive and ignorant."

Thomas Tobin, professor of pharmacology at the University of Kentucky and one of the country's foremost experts on drugs and horses, said that most of the common objections to Bute and Lasix were based on misinformation. mIn particular, he rejected the notion that Bute takes away horses' ability to feel pain so that they keep running until they break down. "Butazolidin only normalizes the inflamed area," Tobin said. "There will still be a perception of pain."

The ban on the drugs will go into effect at the start of 1980 if the state legislature's Committee for Administrative, Executive and Legislative Review approves it in the form of an emergency measure. Otherwise, the effective date might be delayed a few weeks.

But when Bute and Lasix are outlawed, few horsemen believe that date will mark the end of drug use at Maryland tracks. There is such economic pressure on trainers and owners to get their sore-legged horses to the post that some of them still will seek chemical assistance in doing it.

"Now you give everybody the same advantage," said Anthony Chamblin, executive director of the national HBPA. "But when these drugs are prohibited, the unscrupulous trainers will use something else. They will be looking for exotic new drugs which the chemists can't find. We may be going back to the 1960s, when some trainers were using any kind of drug they could get away with."