Jan. 8, 2007 -- Canadian researchers say there is still far too little information about the long-term safety and effectiveness of three major weight lossweight loss drugs.
The researchers say major questions remain about the long-term safety of the obesityobesity drugs Meridia, Xenical, and Acomplia, and they argue that very little research is being done to answer these questions.
Meridia was approved by the FDA in 1997; Xenical won approval in 1999. Acomplia, also known as rimonabant, has not yet been approved for sale in the U.S., but it is available in Europe.
The three drugs act in very different ways. Meridia targets specific chemicals in the brain to reduce appetite, while Xenical helps prevent the absorption of fats from the foods users eat. Acomplia targets what is thought to be the brain's pleasure center to reduce food cravings.
Raj S. Padwal, MD, and Sumit R. Majumdar, MD, reviewed the research that has been done on the three antiobesity drugs, and concluded that the clinical trials have been limited by high drop-out rates among study participants and a lack of long-term data on illness and death.
Their findings appear in the Jan. 6 issue of the journal The Lancet.
"We have a good idea of how much weight loss to expect on average with these medications," Padwal tells WebMD. "But there is a lot we still don't know. If people are going to be put on these drugs long term we really need to know if they are doing more net benefit than harm."
Weight Loss Is Modest
Two-thirds of Americans are overweight or obese and one-third qualify as obese, according to the CDC. Worldwide, the International Obesity Task Force estimates that 1.1 billion people are overweight or obese.
"There is no other condition out there that affects so many people," he says. "That is why the search for effective treatments is so important."
In terms of promoting weight loss, none of the three drugs performed significantly better than the others in the clinical trials, which lasted up to four years. That weight loss could be characterized as modest, at best, Padwal says.
Studies suggest that Xenical can help lower cholesterol and reduce diabetesdiabetes risk, but Padwal and Majumdar conclude that it should probably be avoided by people with chronic diarrheadiarrhea.
Some studies have found a slight increase in blood pressure associated with Meridia use, so the researchers conclude that it should not be prescribed to people with poorly controlled high blood pressurehigh blood pressure "until further efficacy and safety data are available."
Meridia Trial Under Way
A large, ongoing trial evaluating Meridia in overweight patients with heart diseaseheart disease should provide some answers. Results from the study are expected in 2008.
Endocrinologist Holly Wyatt, MD, of the University of Colorado Health Sciences Center, says she is not overly concerned about the long-term safety of the prescription weight loss drugs that are now on the market.
"It is true that we don't have clinical trials that follow users for a decade or more, but we have as much data about the long-term safety of these drugs as we do about many other drugs that have been approved," she tells WebMD. "We have solid studies lasting from two to four years."
Meridia is made by Abbott Laboratories. Xenical is made by Roche Laboratories. Acomplia is made by Sanofi-Aventis. All three companies are WebMD sponsors.
WebMD attempted to contact all three manufacturers of the drugs.
A spokesperson for Abbott Laboratories says the company is committed to doing the kind of research called for in the review and pointed to the ongoing trial evaluating Meridia.
Roche Laboratories and Sanofi-Aventis did not respond to requests for comment.