The current recommendations for the treatment of obese people include increased physical activity and reduced calories intake. When the behavioral approach is not sufficient, a pharmacologic treatment is recommended.

Pharmacotherapy for obesity is indicated for individuals with a BMI greater than 30 kg m2 or BMI greater than 27 kg m2 with at least one obesity‐associated comorbid condition.

Current and potential anti-obesity drugs may operate through one or more of the following mechanisms:

  • Catecholamine releasing agents such as amphetamine, phentermine, and related substituted amphetamines (e.g., bupropion) which act as appetite suppressants are the main tools used for the treatment of obesity.
  • Increase of the body's metabolism.
  • Interference with the body's ability to absorb specific nutrients in food. For example, Orlistat.

In past years, numerous drugs have been approved for the treatment of obesity; however, most of them have been withdrawn from the market because of their adverse effects. In fact, amphetamine, rimonabant and sibutramine licenses have been withdrawn due to an increased risk of psychiatric disorders and non-fatal myocardial infarction or stroke.

Weight loss drugs include: 


Even if orlistat is not as effective as other drugs in reducing body weight, orlistat is presently the only available choice for the treatment of obesity because of its safety for cardiovascular events and positive effects on diabetic control.

Orlistat acts as a peripheral pancreatic lipase inhibitor, and prevents the absorption of fats in the intestine. The side effects may be: steatorrhoea, gastrointestinal discomfort, and reduced absorption of fat soluble vitamins. However, steatorrhea and gastrointestinal discomfort occur particularly in patients who are unable to reduce the daily intake of fat. In patients on warfarin treatment coagulation must be monitored because of reduction in absorption of vitamin K.

Phentermine /topiramate

Phentermine and topiramate, sold under the trade name Qsymia, is a combination medication used for weight loss. Phentermine and topiramate is associated with modest weight loss when compared with placebo. This weight loss was associated with improvements in weight-related comorbidities such as improved blood sugar, decreased blood pressure, and improved cholesterol.

Phentermine and topiramate can cause fetal harm. Data from pregnancy registries and epidemiology studies indicate that a fetus exposed to topiramate in the first trimester of pregnancy has an increased risk of oral clefts (cleft lip with or without cleft palate). If a patient becomes pregnant while taking phentermine/topiramate ER, treatment should be discontinued immediately, and the patient should be apprised of the potential hazard to a fetus. Females of reproductive potential should have a negative pregnancy test before starting phentermine/topiramate ER and monthly thereafter during phentermine/topiramate ER therapy. Females of reproductive potential should use effective contraception during phentermine/topiramate ER therapy.


Lorcaserin is indicated as an adjunct to a reduced-calorie diet and increased physical activity for the chronic weight management in adults with an initial BMI of 30 kg/m2 or greater (obese) or 27 kg/m2 or greater (overweight) in the presence of at least one weight-related comorbid condition (ie, hypertension, dyslipidemia, type 2 diabetes).
Lorcaserin reduces appetite by activating a type of serotonin receptor known as the 5-HT2C receptor in a region of the brain called the hypothalamus, which is known to control appetite.


Sibutramine reduces food intake and body weight and has positive effects on the lipid profile (mainly triglycerides and high density lipoprotein cholesterol), glycemic control and inflammatory markers in studies for up to one year. Preliminary studies showed that sibutramine may also improve other obesity-associated disorders such as polycystic ovary syndrome, left ventricular hypertrophy, binge eating disorder and adolescent obesity. The high discontinuation rates and some safety issues mainly due to the increase in blood pressure and pulse rate have to be considered. Additionally, it has not yet been established that treatment with sibutramine will reduce cardiovascular events and total mortality.


Metformin is an oral anti-hyperglycemic agent that has been demonstrated to be efficacious in the treatment of diabetic and non-diabetic obese adults. Metformin limits the amount of glucose that is produced by the liver as well as increases muscle consumption of glucose. It also helps in increasing the body's response to insulin. However, little is known regarding the effects of metformin, along with diet and exercise, on other measures associated with cardiovascular risk and inflammatory biomarkers.

Other weight loss drugs have also been associated with medical complications, such as fatal pulmonary hypertension and heart valve damage due to Redux and Fen-phen, and hemorrhagic stroke due phenylpropanolamine. Many of these substances are related to amphetamine.

Some patients find that diet and exercise is not a viable option; for these patients, anti-obesity drugs can be a last resort. Some prescription weight loss drugs are stimulants, which are recommended only for short-term use, and thus are of limited usefulness for extremely obese patients, who may need to reduce weight over months or years. 

Because of potential side effects, and limited evidence of small benefits in weight reduction especially in obese children and adolescents, it is recommended that anti-obesity drugs only be prescribed for obesity where it is hoped that the benefits of the treatment outweigh its risks.

The side effects are often associated with the medication's mechanism of action. In general, stimulants carry a risk of high blood pressure, faster heart rate, palpitations, closed-angle glaucoma, drug addiction, restlessness, agitation, and insomnia.

Another drug, orlistat, blocks absorption of dietary fats, and as a result may cause oily spotting bowel movements (steatorrhea), oily stools, stomach pain, and flatulence. A similar medication designed for patients with Type 2 diabetes is Acarbose; which partially blocks absorption of carbohydrates in the small intestine, and produces similar side effects including stomach pain and flatulence.

Few medications are available for the management of obesity but don't replace physical activity or healthy eating habits as a way to lose weight.

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