A consumer group, citing a rising death toll among arthritis sufferers who have taken the drug Oraflex, has threatened to sue the Department of Health and Human Services unless it bans the drug in the next seven days.

Public Citizen's Health Research Group had urged the Food and Drug Administration to withdraw the drug last month, citing reports in British medical journals that the drug had been implicated in 12 deaths in that country.

Yesterday, in a new, more strongly worded petition to Health and Human Services Secretary Richard S. Schweiker, the group said the death toll in Great Britain, where the drug has been available for two years, had risen to 45. Dr. Sidney Wolfe, the group's director, said at least one and possibly four Oraflex users had died in this country since the drug came on the market less than three months ago.

A spokesman for the FDA, which had granted approval to Oraflex April 19, said that the agency was investigating the British and American deaths and that it would withdraw the drug "if it proved necessary." But the spokesman said, "I don't think it is clear that the deaths were caused by Oraflex, especially where the patients were taking other drugs for other diseases."

The drug's manufacturer, Eli Lilly & Co. of Indianapolis, said in an official statement: "Reports of deaths are clearly a serious matter and Lilly continues to study the facts surrounding them. The incidence of serious adverse reactions with Oraflex are comparable to that of other drugs used to treat arthritis, including aspirin. To this date, no reports have clearly identified Oraflex as a causal agent in deaths and approximately one and a half million patients have taken the drug with demonstrable good result."

Wolfe's group cited the death two weeks ago of a 47-year-old Las Vegas woman who had been on the drug for less than a month. According to her physician, she was on no other drugs when she died, had suffered no illness other than severe arthritis and had been negatively screened for liver disease just three months earlier.

"Clinically, I am certain that the drug caused her death," said her physician, Dr. Michael Rask.

Rask said he had put the woman on the drug at her own request. Since her death, he said, he has taken 35 of his patients who also were taking the drug off it, and has reported his findings to the FDA. "I will not allow any of my patients to take it even if they ask for it by name," he said.

Dr. Ian Shedden, vice president of Eli Lilly's research laboratories, said: "It is too early to say but it seems this American woman had a congenital deformity in her liver which may have been a factor--it is by no means a straightforward case. It is true that patients who have taken Oraflex have died, but there is no proof that the drug caused their deaths."

The woman, who has not been named, is believed to be the youngest Oraflex user to die. In Britain most of the drug-related deaths have been among the elderly, predominantly women.

In addition to the deaths, 4,000 adverse reactions among users of the drug have been reported to the British Committee on Safety of Medicines. The Ralph Nader-supported Health Research Group said the number of deaths in Britain connected with the drug, based on 500,000 users, is equal to the total deaths among the 10 million Americans who have used the 19 or so other arthritis drugs in the same two-year period.

"I am aware that the Eli Lilly Company is exerting great pressure on both the FDA and your office not to ban this deadly drug," Wolfe wrote Schweiker.

"It is time for you to quickly decide whether it is more important to protect the financial health of Lilly or to spare the lives of patients, mainly the elderly, in this country. If you have not responded to our petition by the end of this month, we will file suit in the federal District Court to force you to follow the laws instead of the pressures of a large company," Wolfe wrote.

Wolfe said that the claims made by the manufacturer for the superiority of the drug were "outrageous" and that there was "no evidence that Oraflex is any better than aspirin for treating arthritis."

Eli Lilly's 1981 sales were $2.7 billion, and nearly half of that, $1.6 billion, was from its pharmaceutical products.