PORTLAND, Ore. (AP) -- Police trained to detect drugged drivers worry that too many motorists drive with legal sedating medications, such as pain killers, cold and flu treatments and antihistamines.

"It’s one of the weaknesses in our law," said Lt. Chuck Hayes, a 24-year Oregon State Police veteran and a drug recognition specialist.

More than 300 experts from the United States and Canada are in Portland through Tuesday for a national conference. Joining them will be about 100 prosecutors, toxicologists and highway safety advocates.

Hayes would like to see Oregon join Washington state in adding legal drugs to the definition of driving under the influence.

Hayes, who hopes a such a law will be passed by the next Legislature, said the goal is not to punish people but to educate them.

An estimated 400,000 allergy sufferers live in Oregon, studies show. For many, antihistamines alleviate sneezing and watery eyes, but they also can cause drowsiness.

Dr. Robert Julien, an anesthesiologist at Providence St. Vincent Hospital in Portland, said decongestants and blood pressure medication also can cause dizziness, drowsiness and disorientation.

Julien said some medications have the opposite effect.

Anti-asthma medications can cause anxiety reactions and irritability, he said, making overmedicated drivers could become more volatile or hyperactive.

Ruth Vandever, executive director of the Oregon Board of Pharmacy, said she doesn’t think over-the-counter drugs pose a driving hazard as long as the consumer follows the directions on the label.

That means taking the prescribed dosage and, in many cases, not combining the drug with other drugs or alcohol.

"I don’t think it’s anything where the consumer would be disabled by the medication," Vandever said.

Julien acknowledges a lack of research on how the level of such drugs in the blood correlates with behavior. Because of that, he doubts legislation controlling the use of medications while driving would take hold in Oregon immediately.

Julien noted that the use of drug recognition experts in police agencies still is relatively new.

Twenty-five officers underwent Oregon’s first training in 1995 to identify illegally drugged individuals.

Today 120 officers have gone through the 100 hours of drug-recognition training.

"Our goal is to have a drug recognition expert be able to respond to any given area throughout the state at any time," he said.

Oregon law does not permit officers to require urine tests to determine drug use. But the officers have had an 88-percent success rate in convincing the drivers to take the test, Hayes said.

"All of this has to do with the quality of the people we have in the program and their demeanor," Hayes said.

"Forty-five percent of all the urine tests that we get back show two or more drugs in the system."

Once these expert officers have determined that a driver may be drug-impaired, toxicology tests have proved their suspicions right 90 percent of the time, slightly better than the national average, Hayes said.