A variety of prescription drugs worth about $1.5 million in the illegal drug market were fraudulently obtained from Montgomery County pharmacists last year, according to a report released yesterday by the county police department.

The report, the first ever to chart the scope of prescription drug fraud in Montgomery, said the painkillers Dilaudid, Percordan and Morphine, which can give users a heroin-like high, ranked at the top of the list of illegally obtained drugs.

Next most popular among illegal prescription drugs were such sedatives as Quaalude and Seconal, the tranquilizer Valium and various stimulants, the report said.

The report was compiled by the two-year-old pharmaceutical section of the Montgomery police department, which handled 667 cases of prescription drug fraud in 1978.

The 73 people arrested as a result of the unit's work came from the full range of economic, social and professional levels represented in Montgomery County, according to Cpl. Robert Rhodes, who head the unit.

One, a 41-year-old doctor from Preston, Md., whose practice had fallen off, told police he had become addicted to norcotics. He was arrested in a White Oak pharmacy last year as he was trying to obtain 1,000 tablets of phenobarbital with prescriptions he had written for nonexistent patients.

Another person arrested by the unit was a 26-year-old Bethesda woman from a well-known local business family. Rhodes said the woman, who had a 6-month-old child at the time of her arrest, allegedly became addicted to amphetamines after her doctor prescribed weight control pills following her pregancy. The woman is scheduled to be tried in September on charges on obtaining and possessing a controlled dangerous substances.

Her scheme was to call local pharmacies, for prescriptions, posing as a representative of a doctor's office.

Police also arrested a retired doctor, who posed as a physician doing medical research to obtain painkillers for himself. The doctor eventually died of cancer.

Neither of the two doctors, was prosecuted, Rhodes said. Instead, both had their medical licenses revoked and were enrolled in drug rahabilitation programs.

Rhodes said the local state's attorney's office does not prosecute all the pharmaceutical cases. "An in some cases, I'm inclined to agree," Rhodes said, such as when the offender is an individual who became addicted to drugs as a result of illness.

He said about 80 percent of the cases go to court. Since June 1977, he said, 150 persons had been tried, with about 25 percent receiving jail sentences and only two being acquitted.

The maximum penalty is four years in jail and a $25,000 fine, he said.