Obesity is a major health problem worldwide. Although diet and physical activity 
are crucial in the management of obesity, the long-term success rate is low. 
Therefore antiobesity drugs are of great interest, especially when lifestyle 
modification has failed. As obesity is not an immediate life-threatening 
disease, these drugs are required to be safe. Antiobesity drugs that have been 
developed so far have limited efficacies and considerable adverse effects 
affecting tolerability and safety. Therefore, most antiobesity drugs have been 
withdrawn. Fenfluramine and dexfenfluramine were withdrawn because of the 
potential damage to heart valves. Sibutramine was associated with an increase in 
major adverse cardiovascular events in the Sibutramine Cardiovascular Outcomes 
(SCOUT) trial and it was withdrawn from the market in 2010. Rimonabant was 
withdrawn because of significant psychiatric adverse effects. Orlistat was 
approved in Europe and the United States for long-term treatment of obesity, but 
many patients cannot tolerate its gastrointestinal side effects. Phentermine and 
diethylpropion can only be used for less than 12 weeks because the long-term 
safety of these drugs is unknown. Ephedrine and caffeine are natural substances 
but the effects on weight reduction are modest. As a result there is a huge 
unmet need for effective and safe antiobesity drugs. Recently lorcaserin and 
topiramate plus phentermine have been approved for the treatment of obesity but 
long-term safety data are lacking.