The federal government has authorized use of heroin as a painkiller in controlled studies of cancer patients at Georgetown University's Vincent T. Lombardi Cancer Research Center and at a cancer center in New York City.

The National Cancer Institute is supplying the narcotic and sponsoring the studies that will compare pain-deadening effects of heroin and morphine, the narcotic from which heroin was derived in 1898.

Unavailable legally in this country since 1956, heroin is used as a painkiller in Great Britain, particularly for patients suffering from advanced cancer.

It "might be that [the studies] couldn't have been done" as little as six years ago amid a national urban crime wave blamed by some on the needs of heroin addicts, said Dr. Franco Muggia, associate director for cancer therapy evaluation at NCI's cancer treatment division.

NCI is manufacturing heroin for the tests from opium legally imported for medical use. Both opium and heroin, the latter the stronger of the two drugs, are believed to have drawbacks as painkillers. Heroin can cause constipation and nausea, and patients may need increasingly larger doses to control pain.

"Georgetown wants to look directly at the effects on pain relief and other manifestations," Muggia said. "Whether there's better tolerance [than with morphine] in terms of intestinal problems, in terms of euphoria and in terms of depressant effect. It's being compared to morphine, which is considered one of the best analgesics [painkillers] in terms of severe pain."

Neither the patients in the Georgetown tests -- who must be over 18 years of age and able to understand fully what they are getting involved in -- nor the nurse observers will know whether morphine or heroin is being used at any given time. Nor will they know the doses.

The patients will be asked to describe the severity of their pain before being given the narcotics, and then will be asked to reassess their pain at regular ntervals -- 30 minutes after the injection, an hour afterward and then once an hour for six hours. They will not be given additional pain medication during that time.

Muggia said Memorial Sloan-Kettering Cancer Center in New York has already begun studying the pharmacological properties of heroin to determine, among other things, how it differs from morphine.

Studies in Britain have shown heroin to be effective in controlling the pain of terminal cancer. According to Muggia, however, the British have not done comparative studies of the major narcotics.

Pain is one of the most devastating effects of some forms of cancer, preventing patients who might otherwise be physically able to go about their daily business from functioning on any but the most basic level.

In Britain, heroin is often used as an oral medication, and is sometimes mixed with gin, tranquilizers and other painkillers.

Asked if heroin might not have the same deadening, incapacitating effect on cancer patients it has on addicts, Muggia said "that is probably a matter of dosage, and it's probably a matter of personality, environment and expectation."