The long-term safety and efficacy need to be documented for Xenical, Meridia and Acomplia before doctors can be certain that the benefits of these anti-obesity drugs outweigh the risks, according to a commentary appearing in The Lancetmedical journal.
Xenical (known generically as orlistat) and Meridia (sibutramine) are currently approved for long-term use, while Acomplia (rimonabant), which works by curbing a person's appetite, is under review by the US Food and Drug Administration.
Orlistat reduces weight by an average of 3kg, whereas sibutramine and rimonabant each reduce weight by 4kg-5kg, on average, Dr Raj S Padwal and Dr Sumit R Majumdar, from the University of Alberta Hospital in Edmonton, Canada, note in their article.
However, each of the agents carry potentially important adverse effects, the authors note.
Treatment with orlistat is associated with frequent gastrointestinal side effects, sibutramine may raise blood pressure and heart rate, and rimonabant may increase the risk of mood disorders.
These adverse effects are typically apparent during short-term use.
The greater concern, according to the authors, is what will occur with long-term use.
Dr Padwal and Dr Majumdar said that research on anti-obesity agents was plagued by high drop-out rates and by a lack of data on long-term illnesses and deaths.
"In light of the lack of successful weight-loss treatments and the public health implications of the obesity pandemic, the development of safe and effective drugs should be a priority," the researchers stated.
However, they said anti-obesity drug trials showing important reductions in obesity-related illness and mortality "should be required either before these drugs are approved for widespread use or as a condition of ongoing approval".