Two of America's most heavily advertised drugs -- aspirin and acetaminophen (the drug in Tylenol and Anacin-3)--may cause serious kidney damage in some persons when used daily for years, a doctor said yesterday.

Other authorities have said there is no evidence that long-term use of aspirin does so, though the jury is still out on long-term use of acetaminophen.

Dr. William M. Bennett of the Oregon Health Sciences University said that "all the answers aren't in." But, he added, "Both doctors and the public have been subjected to massive advertising implying that all these analgesic products are entirely safe for long-term use."

Bennett, professor of pharmacology and head of kidney treatment at the Portland medical school, told a National Kidney Foundation symposium that even a few years of regular use, say six or eight tablets a day, may be enough to cause problems.

"The TV commercials and printed ads carry a caveat--'See your doctor if pain persists'--but this is overwhelmed by the subliminal message that long-term use is absolutely safe," he said. "We are far from sure this is true.

"I don't want to discourage anyone taking analgesics under a doctor's care for an important reason. But I believe they should have an annual checkup of blood pressure and urine, and a blood test for signs of kidney damage, including any buildup of creatinine, a protein that accumulates when the kidneys don't work."

At some centers "as many as 5 to 10 percent" of patients who must have a kidney transplant or go on kidney dialysis are victims of chronic use of painkillers, Bennett said.

"The most important problem," he reported, "is excessive use of over-the-counter drugs for minor aches and pains. The typical patient is a middle-aged woman who starts taking them daily for symptoms like headache or back pain, then continues for years."

Unfortunately, he said, kidney damage often causes no symptoms until damage is severe and perhaps fatal.

Doctors need to know more about preventing kidney failure. Yet, Bennett complained, there has been only one long-term, "prospective" study of a painkiller's effect in a sizable population over time. Doctors followed 623 working women aged 30 to 49 who used the anti-pain drug phenacetin. Over 11 years, 33 died, three times the death rate of a similar group of non-phenacetin users.

Phenacetin, until recently an ingredient in Anacin, APCs, Excedrin, Bromo-Seltzer and many other compounds, is being banned by the Food and Drug Administration, starting next August.