There are few options for drug therapy of obesity. Today, the FDA-approved drugs for the long-term treatment of obesity are Orlistat (Xenical), Lorcaserin (Belviq), and Qsymia, a combination of Phentermine and Topiramate Extended-Release (ER).
The FDA has issued a warning about over-the-counter slimming drugs that contain active pharmaceutical ingredients with unknown content. Such products marketed under the name of “dietary supplement” on many Internet sites and pharmacies have not been approved by the FDA; so, they are illegal and may be potentially quite dangerous. In April 2015, the FDA has forbidden the use of amphetamine-like stimulants (BMPEA) in the production of such supplements. This substance is sometimes added to labels as ‘acacia rigidula’.
Orlistat reduces the ability to digest and absorb triglycerides by blocking the lipase enzyme released from the pancreas. There are two major clinical studies showing that it has provided 9-10% weight loss within 2 years. The efficacy of orlistat on weight loss does not depend on the systemic absorption of the drug. This drug may reduce the absorption of certain fat soluble vitamins (A, D, E, K) and beta carotene. It may also affect the absorption of certain medicines. Its side effects include steatorrhea (excess fat in stool), frequent defecation, fecal incontinence and increased intestinal gas.
This drug was approved by the FDA in June 2012 for use in people with a body mass index (BMI) of 30 or greater, in addition to a low-calorie diet and exercise program. It is a Group 4 drug, i.e. a drug that potentially poses a risk of addiction. Lorcaserin is thought to limit food consumption by creating the feeling of satiety by means of some receptors in the hypothalamus. It has been approved based on three important studies showing that the drug has provided 5% and more weight loss with a 1-year treatment and maintained the result for a period of 2 years.
Since the studies conducted in the later period suggest that it may have serious cardiac side effects, it should be carefully used in patients with heart failure.
Liraglutide is analogous with GLP-1 (glucagon-like peptide-1), the physiological regulator of appetite and caloric intake. GLP1 receptors are available in many regions of the brain. This drug has been approved for use in obese people with a body mass index (BMI) of 30 or greater, in addition to diet and exercise for chronic weight management. Its dose used for obesity is different from that used for diabetes (Victoza). The dose should be gradually increased from 0.6 mg to 3 mg.
The approval of liraglutide is based on 3 clinical studies conducted on 4.800 obese patients. It has provided 4.5% weight loss within 1 year. This rate is 3.7% in the control group. 34% of patients, on average, have lost at least 5% of their body weight.
Phentermine and Topiramate
The combination of these two substances has been approved by the FDA in June 2012 for use in people with a body mass index (BMI) of 30 or greater. Its use in pregnant women is contraindicated. Topiramate is actually is a drug first licensed as an antiepileptic compound. Serious weight losses up to 5-7% were observed in the patients. The degree of weight loss increases in parallel with the initial weight. The mechanism of this effect is still under investigation. Its efficacy degree is impressive; however, it has certain side effects such as sleepiness, paresthesia, memory loss and confusion.
Qsymia contains the extended-release form of topiramate. In addition, the topiramate dose (46-92 mg) in this drug is considerably lower than the dose used for epileptic seizures (200 mg, twice daily).
Drugs Used for Short-Term Treatment
There are 4 agents used in the United States: diethylpropion, phendimetrazine, benzphetamine, and phentermine. These drugs should be used in combination with caloric limitation in people with a body mass index (BMI) of 30 or greater.
Drugs with Different Indications
Some drugs used for totally different diagnoses are also used in bariatric treatment, since they trigger weight loss. This group includes some antidepressants such as selective serotonin re-uptake inhibitors (SSRIs). Drugs used for this purpose:
-Methylphenidate: It has not been approved by the FDA for bariatric treatment (obesity treatment); however, there are various studies showing that it has been successful.
-Zonisamide: When Gadde et al. used these antiepileptic drugs on 60 obese patients, they reported very few side effect profiles and stated that they achieved about 6% weight loss.
-Octreotide: Lustig et al. reported the potential benefits of this drug in certain subgroups of hypothalamic obesity.