An increasing number of Americans in all social classes are using cocaine, becoming addicted to it and even dying from overdoses, the President's Commission on Organized Crime was told yesterday.

Expert witnesses challenged the popular notion that cocaine is a nonaddictive drug that can be used without serious consequences.

"What is a safe dose one day can become a fatal dose the next," said Dr. Charles Wetli, deputy chief medical examiner of Dade County (Miami), Fla.

Several psychologists, four previous cocaine users and two Drug Enforcement Administration officials also testified before the commission as it shifted its attention to drug use after earlier hearings on mob activity.

Wetli said he began performing autopsies on cocaine victims in 1969. The incidence of sudden death due to recreational use of cocaine has risen in Dade County from one or two per year in the early 1970s to about two per month this year, Wetli testified. Most victims injected the drug into their veins, he said.

"In a typical cocaine overdose death, the first 30 to 60 minutes after taking cocaine are without problems. Then the victim undergoes seizures, respiratory collapse and death," Wetli testified while pictures of overdose victims were projected on a screen.

In other cases, Wetli said, cocaine users develop a rapidly fatal infection of the brain. In still other cases, in which the exact mechanism of death is not understood, the cocaine user has a "psychotic reaction," exhibits bizarre behavior such as jumping through windows or taking off all his clothes in public, is restrained by police and dies within an hour.

Another expert testified that a vast number of Americans in all social classes use cocaine, partly because of its increased availability and decreasing cost. Between 5 and 6 million Americans say they use cocaine at least once a month, but the number of regular users is probably closer to 10 million, according to Arnold Washton, director of substance-abuse research and treatment at The Regent Hospital in New York City.

"If ever there was a drug that fit the tenor of the times, cocaine is it, just like marijuana was the drug of the 1960s," Washton testified.

Washton said the baby-boom generation that used marijuana in the 1960s to get a "mellow, laid-back" feeling has grown up. Now, he said, people in that age group are "hard-driving business executives. They take cocaine because it makes them feel increased physical, mental and sexual capabilities."

Washton said that while beginning users may feel as though they have increased capabilities, the drug eventually reverses itself. "It makes users feel chronically depressed, not energized, " he said.

Four previous cocaine users each testified that they had been addicted to the drug. One, Keith O'Malley, a former police officer, said he had used cocaine daily in the squad car. When stopping cars for traffic violations, he said, he sometimes found drugs in the car. "I'd obtain the drugs and let him the driver or passenger go free," O'Malley testified.

O'Malley did not identify the police force he had worked for but said he was dismissed after he was charged with attempted bribery.

Two officials of the Drug Enforcement Administration who had been assigned to Colombia testified that most cocaine comes into the United States on airplanes from South America.

One day before the officials testified, 1,500 pounds of Peruvian cocaine were confiscated and four men were arrested at a remote abandoned airstrip in Kingman, Ariz. Authorities said the shipment could have a street value of up to $5 billion depending on its purity.

Authorities were alerted to the smuggling operation by a vacationing detective, who spotted fresh airplane tracks at the old airstrip.