Weight Loss Drugs

Anti-obesity drugs or weight loss drugs refer to all pharmacological agents that reduce or control weight. These drugs alter one of the fundamental processes of the human body, weight regulation, by either altering appetite or metabolism. It is recommended because of potential side effects that they only be prescribed for obesity where it is hoped that they benefits of the treatment outweigh its risks.

A meta-analysis of randomized controlled trials by the international Cochrane Collaboration concluded that in diabetic patients found:

"Fluoxetine, orlistat, and sibutramine can achieve statistically significant weight loss over 12 to 57 weeks. The magnitude of weight loss is modest, however, and the long-term health benefits remain unclear. The safety of sibutramine is uncertain. There is a paucity of data on other drugs for weight loss or control in persons with type 2 diabetes.

Mechanisms of action

Anti-obesity drugs operate through one or more of the following mechanisms:

Suppression of the appetite. Epilepsy medications and catecholamines and their derivatives (such as amphetamine-based drugs) are the main tools used for this. Drugs blocking the cannabinoid receptors may be a future strategy for appetite suppression.[citation needed]
Increase of the body's metabolism.[citation needed]
Interference with the body's ability to absorb specific nutrients in food. For example, Orlistat (also known as Xenical and Allī) blocks fat breakdown and thereby prevents fat absorption. The OTC fiber supplements glucomannan and guar gum have been used for the purpose of inhibiting digestion and lowering caloric absorption
Anorectics (also known as anorexigenics) are primarily intended to suppress the appetite, but most of the drugs in this class also act as stimulants (dexedrine, e.g.), and patients have abused drugs "off label" to suppress appetite (e.g. digoxin).

Available anti-obesity drugs

If diet and exercise are ineffective alone, anti-obesity drugs are a choice for some patients. 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.[citation needed]

Orlistat

Orlistat (Xenical) reduces intestinal fat absorption by inhibiting pancreatic lipase. Originally available only by prescription, it was approved by the FDA for over-the-counter sale in February 2007. Orlistat may cause frequent, oily bowel movements (steatorrhea), but if fat in the diet is reduced, symptoms often improve.

Sibutramine

Sibutramine (Reductil or Meridia) is an anorectic or appetite suppressant, reducing the desire to eat. Both drugs have side effects. Sibutramine may increase blood pressure and may cause dry mouth, constipation, headache, and insomnia.


Metformin

In people with Diabetes mellitus type 2, the drug metformin (Glucophage) can reduce weight.


Byetta

Byetta (Exenatide) is a long-acting analogue of the hormone GLP-1, which the intestines secrete in response to the presence of food. Among other effects, GLP-1 delays gastric emptying and promotes a feeling of satiety. Some obese people are deficient in GLP-1, and dieting reduces GLP-1 further.[5] Byetta is currently available as a treatment for Diabetes mellitus type 2. Some, but not all, patients find that they lose substantial weight when taking Byetta. Drawbacks of Byetta include that it must be injected twice daily, and that it causes severe nausea in some patients, especially when therapy is initiated. Byetta is recommended only for patients with Type 2 Diabetes. A somewhat similar drug, Symlin, is currently available for treating diabetes and is in testing for treating obesity in non-diabetics.


Symlin

Symlin (Pramlintide) is a synthetic analogue of the hormone Amylin, which in normal people is secreted by the pancreas in response to eating. Among other effects, Amylin delays gastric emptying and promotes a feeling of satiety. Many diabetics are deficient in Amylin. Currently, Symlin is only approved to be used along with insulin by Type 1 and Type 2 diabetics. However, Symlin is currently being tested in non-diabetics as a treatment for obesity. A drawback is that Symlin must be injected at mealtimes.


Rimonabant

Recent pharmaceutical research has produced potential obesity combating drugs. The discovery of cannabinoid receptors in the brain, liver and muscle has stimulated research in a new class of drugs, namely cannabinoid (CB1) receptor antagonists. These drugs not only causes weight loss, but prevent or reverse the metabolic effects of obesity, such as insulin resistance and hyperlipidemia, and may also decrease the tendency to abuse substances such as alcohol and tobacco.

Sanofi-Aventis has received approval to market Rimonabant as a prescription anti-obesity drug in the European Union, subject to some restrictions. Due to safety concerns, the drug has not received approval in the United States, either as an anti-obesity treatment or as a smoking-cessation drug. Merck has a CB1 inverse agonist, taranabant (codenamed MK-0364), in Phase IIb/III development for which it hopes to file a New Drug Application in 2008


Other drugs

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.

Unresearched nonprescription products or programs for weight loss are heavily promoted by mail and print advertising and on the internet. The US Food and Drug Administration recommends caution with use of these products, since many of the claims of safety and effectiveness are unsubstantiated. Individuals with anorexia nervosa and some athletes try to control body weight with laxatives, diet pills or diuretic drugs, although these generally have no impact on body fat. Products that work as a laxative can cause the blood's potassium level to drop, which may cause heart and/or muscle problems. Pyruvate is a popular product that may result in a small amount of weight loss. However, pyruvate, which is found in red apples, cheese, and red wine, has not been thoroughly studied and its weight loss potential has not been scientifically established.


Side effects

Some anti-obesity drugs have severe and often life-threatening side effects. (See, for example, Fen-phen.) These side effects are often associated with their 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.