Weight loss drugs refer to specific medication, produced and marketed, for reduction or control of weight. They work by either reducing appetite, blocking absorption of calories or by altering the body’s metabolism of energy.

Some individuals try to control body weight with laxatives or diuretics but there is no evidence that they have an impact on body fat and they have a number of serious side effects particularly on disorders of blood chemistry.

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Safety and potential side effects of weight loss drugs represent one of main issues regarding their widespread availability. It is also important to understand that the explosion of medical research in this area has not yet generated such a wide range of clinical products with clearly documented health benefits. Serious concerns about the cardiac and mental health safety of some appetite suppressantshas resulted in the suspension of a number of agents previously marketed.

Amphetamines.

These medications have been widely used in the past as appetite suppressants. They were the most effective diet pills and the most popular for decades from about the 1930’s. When in 1979 it became clear that a number of deaths were associated with their use, amphetamines in diet pills were banned by the FDA.

Fenfluramine (Fen-phen) and then dexfenfluramine (Redux) were popular in the 1990’s but these too were withdrawn from the market in 1997 following overwhelming evidence that they cause valvular heart disease in a relatively high percentage of those who had taken them.

Thyroid Hormones.

Many people ask about the use of the thyroid hormone, thyroxine, as a means of weight loss. Its possible effectiveness is based upon the presentation of patients with an underactive thyroid and weight gain with its subsequent resolution on thyroxine treatment.

Historically, thyroxine has been used as a weight-lowering agent but it is not now considered safe to do so. There is conclusive evidence that increasing blood thyroxine in healthy people to levels that increase metabolism enough to result in weight loss will also cause side effects such as palpitations, cardiac arrhythmias and osteoporosis.

Rimonabant

(Acomplia): This interesting drug was developed from research on the brain receptor activated by cannabis. It acts by decreasing appetite. Weight loss was shown to be greater than other available medication. For people with diabetes there were added advantages in that the drug also improved insulin resistance.

The drug never received approval in the United States due to safety concerns regarding psychiatric related side effects. In Europe the drug was available for a short time but was withdrawn in 2008 when these safety concerns were substantiated.

Sibutramine

(Reductil): This once daily appetite suppressant was available in the recent past in the UK for the treatment of obesity. Although it’s potential to increase the blood pressure of some patients was well known there are now more serious concerns regarding this drugs potential to cause cardiovascular disease.

The concern is that sibutramine increases the risk of heart attacks and strokes in patients with a known or high risk of cardiovascular disease. For this reason sibutramine has been suspended from use in the UK. On January 21st 2010 the European Medicines Agency recommended suspension of marketing authorizations for sibutramine.

Orlistat

(Xenical and Alli): Orlistat reduces intestinal absorption of fats from the diet and thereby reduces calorie intake. It has been available for many years as a prescription only drug under the trade name Xenical (120 mg tablet). More recently an over the counter version has been available under the trade name Alli (60 mg tablet). Now that the use of sibutramine has been suspended Orlistat remains the only available prescription drug specifically for the management of weight loss on the UK formulary.

The easy availability of over the counter Orlistat has generated quite a lot of controversy. Many doctors are concerned that potential serious side effects such as liver toxicity may occur unmonitored. There are also drug interactions to consider such as the altered metabolism of the anti-transplant rejection drug cyclosporine or the anti-arrhythmic heart drug amiodarone. Also the absorption of fat-soluble vitamins is inhibited by Orlistat raising concerns about vitamin deficiencies in people taking the drug over long periods of time.

Orlistat is effective in promoting weight loss. Statistics indicate an extra 2-3 Kg weight loss over time in people taking the drug compared to those just following the recommended changes in diet and exercise. Although this effect cannot be considered particularly dramatic, a large-scale clinical trial also indicated a significant reduction in the incidence of diabetes in obese subjects taking Orlistat. The main barrier to using Orlistat is the well-known gastrointestinal side effect of oily loose stools and in some cases urgent bowel movements or even faecal incontinence. This results from the decreased fat absorption and therefore increased fat load in the intestine. Knowledge of this encourages the user to follow a lower fat diet.

Counterfeit diet supplements.

The World Health Organization has drawn attention to the very significant amount of counterfeit medication, which circulates the global market. In 2008 the FDA alerted consumers to the variety of ‘dietary supplements’ for weight loss that contain illegal and undisclosed substances.

There have been a number of research articles highlighting the addition of sibutramine in so called herbal supplements sold in Europe. A similar alert has been issued regarding counterfeitversions of over the counter weight loss drug Alli sold over the internet. It was found to contain sibutramine at concentrations at least twice the amount recommended.