Pharmacotherapy for Obesity

Pharmacotherapy for Obesity

Weight Loss Tablets

Throughout the ages people have tried pills and potions to help them lose weight. Today, there are 3 types of medically approved, clinically tested weight loss tablets available on prescription: Orlistat (trade name: Xenical), Sibutramine(Reductil) and Rimonabant (Acomplia). A number of others are currently in development by the pharmaceutical companies.


Amphetamines-based drugs (e.g. Fenfluramine) have been used in the past as weight loss agents. Although successful at producing weight loss, these medications can be highly dangerous and have resulted in a number of deaths. As a result, they should not be used. Occasionally, amphetamine-based products are offered by disreputable clinics or by internet sites. It cannot be stressed enough how dangerous this practice is. Amphetamine-based products should be avoided!


Herbal remedies

Herbal medicines are sometimes suggested as an alternative therapy. These are unproven and, more importantly, have not been the subject of studies to investigate their safety. In addition there have been cases of unscrupulous vendors incorporating tablets, including amphetamines, into powders and tablets marketed as ‘hernal remedies’. Buyer beware!


It is important to recognise that tablets are not an alternative to adopting a healthier diet and lifestyle, but help these changes to be more effective. Tablets will not work unless combined with dietary changes and increased physical activity. The pharmaceutical companies that produce these tablets are aware of this and provide support packages that accompany the medication. There is good evidence that people who enrol in these support schemes are more successful at losing weight than those who do not. Given this we would encourage all those who start using these tablets to enrol in the accompanying support scheme. Details are provided when these tablets are prescribed.


In each box of tablets prescribed there is a detailed information sheet about that medicine, how it works, who should and who should not take it, side effects associated with the drug and whether it interferes with the action of other tablets. Your doctor will be aware of this information and will have based the decision to prescribe the medication on this. This information is there for your benefit and we would recommend reading this if you require detailed information about any medication you take. However, these information sheets are by their very nature extremely detailed and there is the danger of information overload. In addition, just because a potential side effect is listed, it does not mean that it is likely to occur. Indeed, most side effects are rare. This site provides a succinct practical review of weight loss medication based on practical experience.


Orlistat (Xenical)

Orlistat is a lipase inhibitor. Lipase is the digestive enzyme which breaks down fat. Therefore, one Orlistat tablet (120 mg) is taken before each meal. This reduces the amount of fat which is digested and absorbed by the body. Even the best ‘low fat’ diet will contains some fat and fat is very high in calories. Orlistat reduces the amount of fat absorbed and therefore reduces the amount of calories absorbed. It therefore helps towards keeping to a reduced calorie diet.


Very little Orlistat is absorbed into the blood stream so Orlstat is very safe. Unfortunately, this does not mean that is free of side effects. The fat which is not absorbed by the body must come out somewhere and often does so as an oily diarrhoea. This is a common side effect of Orlistat.


Like any treatment, some people response better to Orlistat than others. Nevertheless, studies suggest that Orlistat is the least powerful of the weight loss medications available. Some suggest that the average weight loss is about 3% of the starting weight.


So safe is Orlistat that it may soon be possible to buy it over the counter (without the need for a prescription). If so, this would be at the lower dose of 60 mg per tablet with a suggested dose of one tablet with each meal. Although this dose is lower there are suggestions that it may be almost as effective as the higher dose Orlistat but without causing as many problems with diarrhoea.


Sibutrmine (Reductil)

Sibutramine is a completely different type of drug to Orlistat. Sibutramine works mainly on the brain and inhibits the re-uptake (and by doing so increases the effect) of two chemicals (noradrenaline and serotonin) which nerve cells use to communicate with each other. This is the same way in which many anti-depressants work. It is no surprise to find out, then, that Sibutramine was original developed to be an anti-depressant. Unfortunately it did not work very well as an anti-depressant, but it was noticed that people who took it lost weight. It is thought that it works mainly by making you fell fuller quicker (or put technically, by enhancing satiety). It probably has other metabolic effects as well.


Studies suggest that it is usually more effective than Orlistat and does not cause diarrhoea. There have been suggestions that it may cause a small increase in blood pressure. Because of this, it is recommend that if you start taking Sibutramine that you have your blood pressure checked fortnightly for the first 3 months, then once a months for a further 3 months, and then once every 3 months after that. This puts off a lot of people, including GPs who have to do the blood pressure monitoring. This blood pressure effect of Sibutramine has long been questioned and there is now some evidence that successful Sibutramine use may actual lower blood pressure. However, despite this, doctors are still cautious in using it in patients who have a problem with high blood pressure.


A rare side effect of Sibutramine is that is can produce abnormal heart rhythm in patients who are susceptible to this. Therefore, if you have had problems with palpitations, this is probably not the treatment for you.


Also, Sibutramine should not be used by someone who is also taking antidepressant tablets.


Those who are eligible for Sibutramine usually find that is works well and is problem free. It is usually taken at a dose of one tablet per day (either 10 mg or 15 mg).


Rimonabant (Acomplia)


The newest of the weight loss tablets, and probably the most powerful, is rimonabant. This works by partially blocking the action of some of the body’s natural chemical signals (called endocannabinoids). The development of rimonabant is very interesting. It has been known for a long time that cannabis abusers get hungry (or ‘get the munchies’). Of course, the body has not developed receptors to respond to cannabis, so the cannabis most be acting on a receptor which is really there to receive a different chemical signal, one which the body makes itself (called an endocannabinoid). This receptor was identified by clever scientists.and called CB1. It was realised that if a drug could be developed which partially blocked CB1 then this should have the opposite effect on appetite to cannabis, namely it should make people less hungry. Hence the development of rimonabant, the first CB1 receptor blocker.


It was initially thought that CB1 receptors where really only found in the brain. However, we now know that CB1 receptors are found throughout the body. Blocking these seems to block some of the harmful signals which fat cells produce. For example, diabetic patients who lose weight taking rimonabant find that their diabetic control improves about twice much as can be accounted for by the weight loss alone (yes, type 2 diabetics can improve their diabetes simply by losing weight!).


Rimonabant is usually tolerated well without causing much in the way of side effects, apart from some nausea. However, there have been concerns that it may cause depression. There is certainly good evidence that if a person has been troubled with depression in the past, then taking rimonabant can cause a recurrence. Because of this, rimonabant is contra-indicated (can not be used) in those who have suffered from depression. But if you have not suffered from depression, the chance of rimonabant causing depression is very small.

Translate »