The most popular prescription sleeping pill in the world was banned in Britain yesterday because of safety concerns, but the U.S. Food and Drug Administration said it had no immediate intention to follow suit.
Although the drug, Halcion, has been the focus of a growing debate regarding its side effects over the last two years, health officials in this country were surprised by the British prohibition. They said they knew of no new studies that would shed light on the medication, which has been linked at times with memory loss and violent behavior.
"We don't know why they did this, but we take it seriously and we're looking into it," said Eva Kemper, a spokeswoman for the FDA.
The drug, also called triazolam, is made by the Upjohn Co., based in Kalamazoo, Mich. It belongs to a class of drugs related to Valium called benzodiazapines, which are used to treat insomnia, anxiety disorders and as part of general anesthesia. They have all been associated with numerous adverse reactions from amnesia to loss of inhibition.
But in a statement issued yesterday, the British Ministry of Health said that compared with other drugs in this group it now believed that "treatment with triazolam is associated with a much higher frequency of psychiatric side effects, particularly loss of memory and depression."
Jenny Moseley, a spokeswoman for the ministry, said that "information came to light five weeks ago that led us to believe that the risk of this drug outweighed the benefits."
Although she could not be specific, she said the new information related to clinical trials conducted "some years ago" as well as 390 reports from practicing doctors of problems with the drug.
The Food and Drug Administration has received several hundred similar reports from doctors in this country through its adverse drug reporting program.
The unusually high number of complaints set off numerous investigations, including several at the FDA, but all scientific studies have concluded that Halcion is no more dangerous than Valium, Librium or its other relatives.
"There is no evidence that any one benzodiazapine clearly had more adverse effects than others," said Dr. Wallace Mendelson, director of the Sleep Disorder Center at the State University of New York at Stony Brook.
Stuart Yudofsky, chairman of psychiatry at the University of Chicago Medical School, said, "If you ask, 'Is there scientific proof that Halcion is associated with aggressive disorder more than others in its class?' the answer when it is correctly prescribed is no."
But he said there was some evidence that Halcion might cause more memory problems than other medicines in its class. He told of one businessman who took Halcion before flying overnight to Europe and the next day could not remember the four hours he had spent preparing for an important business meeting.
Far more worrisome are the complaints that patients on Halcion are prone to violence. Several years ago Ilo Grundberg, a 57-year-old Utah woman, killed her mother while on the drug and sued Upjohn for damages. The charges against Ms. Grundberg were ultimately dismissed and the drug company settled out of court, vehemently denying that Halcion was to blame.
More than 7 million Americans take Halcion, contributing to the drug's projected sales of $260 million for 1991. Upjohn's stock dropped $2.25 Monday but has since recovered most of the loss, closing up $1.75 at $46.25 on the New York Stock Exchange yesterday.
Upjohn's chairman, Dr. Theodore Cooper, said yesterday, "There is absolutely no scientific or medical evidence that warrants withdrawal of Halcion tablets in the U.K. or any other country."
Experts are uncertain why so many complaints surround Halcion, but many suspect they are largely a function of the drug's popularity, since more patients inevitably means more problems. Others say bad publicity about the drug and a few widely publicized lawsuits have created a snowballing effect.
"It's sort of like the Prozac controversy," Dr. Mendelson said. "If someone has a problem on this drug, even if they're on many others, it is assumed to be at fault."
He said that it is also often difficult to figure out if patient problems are a result of Halcion or the disorder the pill has been taken to combat. Although people on Halcion have complained of memory loss, he notes that in studies about 80 percent of people with insomnia -- who took no medicine -- complained of memory problems as well.
Despite the debate, many psychiatrists believe that Halcion is in many ways safer than its relatives since it is broken down by the body in about five hours. Drugs like Librium and Valium last far longer and are more likely to build up to toxic levels, resulting in daytime drowsiness in patients who took the pills the night before.
Dr. Mendelson and other sleep experts emphasize that all of the Valium-like drugs must be used with great caution, both because of their myriad side effects and because they are potentially addictive.
Dr. Yudofsky said that European doctors in the past tended to use Halcion in doses four times higher than the dose commonly given now in the United States, which he said might explain the greater level of concern on that side of the Atlantic.
In terms of side effects like memory loss and violence, "think of it as the difference between two beers and eight beers," he said.