Obesity and overweight are reaching global epidemic proportions affecting more than 1.1 billion individuals worldwide. Excess weight is associated with an increased mortality, chronic morbidity (including type 2 diabetes, arterial hypertension, cardiovascular diseases, and certain cancers), decreased quality of life, and considerable health care costs.
Antiobesity treatment is recommended for selected patients in whom lifestyle modification is unsuccessful. Two antiobesity drugs are currently for long-term use: Orlistat and Sibutramine.
Generic Xenical (Orlistat), a gastrointestinal lipase inhibitor, reduces weight by around 3 kg on average and decreases progression to diabetes in high-risk patients. Orlistat inhibits intestinal lipase enzymes that are responsible for the digestion of dietary fats. This results in the enhanced excretion of fat in the faeces with subsequently fewer calories absorbed. Most of the side effects reported were related to GI events such as diarrhoea and oily stools, flatulence, bloating, abdominal pain and dyspepsia.
Generic Reductil Sibutramine (Meridia), a monoamine-reuptake inhibitor, results in mean weight losses of 4–5 kg, but is associated with increases in blood pressure and pulse rate. Sibutramine enhances satiation by blocking the reuptake of monoamine neurotransmitters (serotonin, noradrenaline and to a lesser extent dopamine), thereby causing elevated levels of these compunds in the hypotalamus. Common side effects include dry mouth, constipation, and insomnia.
Generic Acomplia (Riomont) is the first in a new class of drugs called CB1 antagonists and reduces weight by 4–5 kg on average. It blocks binding of endogenous cannabinoid to neuronal CB1 receptors. While activation of these receptors by endogenous cannabinoids increases appetite, blocking them in the hypothalamus appears to lower appetite and results in weight loss.
All the drugs are potentially effective when used appropriately and with additional weight-loss measures, including diet, exercise, and behavioural modification.