"Given the modest decrease in body weight associated with sibutramine and the potentially substantial weight regain with discontinuation of therapy, even a small increase in cardiovascular risk seems unwarranted," states Dr. Simone Pinheiro, of the agency's epidemiology division.
In a public hearing Wednesday, an outside panel of experts will weigh in on the course of action FDA should take. The agency is not required to follow the group's advice, although it often does.
Meridia has drawn criticism from public safety advocates for years, and earlier this month the editors of the New England Journal of Medicine called on the FDA to withdraw the pill.
"It is difficult to discern a credible rationale for keeping this medication on the market," the journal's editorial concluded.
Meridia was approved against the majority opinion of FDA's outside advisers, who highlighted the potential for heart problems. The drug later won approval in Europe, though regulators there called on Abbott to study the drug's effect on pre-existing heart conditions.
The research involved about 10,700 overweight or obese people 55 or older who had heart disease, diabetes or both and were treated for about 3 1/2 years. According to results issued late last year, patients taking Meridia had a slightly higher risk of heart attack, stroke or other fatal heart problems than those taking placebo.
European regulators withdrew the drug from the market on the results, while the FDA bolstered the drug's warning label, underscoring the risks to patients with heart problems. In the U.S. the drug is contraindicated for patients with a history of heart disease, though prescribers do not always follow such guidelines.
A large portion of the FDA's analysis issued Monday analyzes data from the 10,000-patient study. Since trial enrollees already had a history of heart disease, several scientists said it was difficult to parse out which heart problems were caused by the drug.
But another FDA reviewer points out that deaths continue to be reported with the drug in young patients with no history of heart problems.
"Young people without known risk factors, aside from obesity, have died shortly after initiating sibutramine therapy," states the review from the FDA's office of surveillance, which monitors adverse events reported with drugs.
Abbott spokesman Scott Davies said Monday that the average age of U.S. Meridia users is 44, so any adverse events reported with the drug would be among relatively young patients. Davies said the North Chicago-based company will use Wednesday's meeting to suggest "risk management measures to ensure that the drug is used in the appropriate patient population."
Meridia use in the U.S. has been steadily declining in recent years, according to prescription data firm IMS Health. About 283,000 prescriptions for it were filled last year, just more than half the number of prescriptions in 2005.
Abbott doesn't actively promote Meridia in the U.S., according to Davies. The company expects global sales this year to be less than $100 million, including less than $30 million in the U.S., he said.
With U.S. obesity rates nearing 35 percent of the adult population, doctors and patients say new pharmaceutical treatments are needed.
But weight loss drugs have long been plagued by negative side effects -- particularly heart problems. In the same year Meridia was approved, Wyeth's diet drug combination, fen-phen, was pulled off the market because of links to heart-valve damage and lung problems.
The FDA is reviewing a new generation of diet pills. On Thursday, the same FDA panel will review a new weight loss pill from Arena Pharmaceuticals. Studies of the drug, lorcaserin, have been free of the heart problems seen with older drugs.