A benefit-risk assessment of sibutramine in the management of obesity

Development and validation of a high-performance thin-layer chromatography method for detection of sibutramine in dietary supplements

INTRODUCTION

In the period between 1997 and 2010, sibutramine-containing drugs were widely prescribed for obesity and over-weight management. Due to safety concerns, in 2010 all medicines containing sibutramine were urgently withdrawn from the USA and European pharmaceutical market. Although sibutramine is no longer available in pharmaceutical products, there have been numerous reports of mislabeled weight-loss dietary supplements containing sibutramine.

Comprehensive traditional East Asian medicine treatment strategy for obesity considering the therapeutic effects and adverse events: A protocol for systematic review and network meta-analysis

BACKGROUND

Obesity has become a serious global health problem due to its increasing prevalence. Because of several limitations or adverse events associated with conventional western medicine therapies, there has been an increase in demand for alternative therapies such as traditional East Asian medicine (TEAM). This study aims to provide comprehensive evidence-based information assessing the clinical efficacy and safety of TEAM treatment for obesity as the basis for reliable clinical strategies for patients with obesity.

METHODS

Electronic searches of the PubMed, Cochrane Library, EMBASE, China National Knowledge Infrastructure, OASIS, and Korea Citation Index will be performed. Methodological quality will be assessed using the "risk of bias" tool. The primary outcome for efficacy will be weight loss. The secondary outcomes will be response rate, body mass index, waist circumference, and blood pressure. We will also evaluate the rates of adverse events and mortality for safety assessment. First, we will conduct a conventional pairwise meta-analysis. Next, we will conduct network meta-analysis using the frequentist approach. We shall verify the assumption of network meta-analysis and provide network geometry, P-score, net league table, and intervention-based forest plot. A subgroup analysis will be conducted to ascertain the factors that affect treatment, such as dosage, treatment duration, and severity of obesity.

RESULTS

The results of this study will provide high-quality systematic reviews that can assist decision making in obesity management. Our network meta-analysis results can provide direct and indirect comparison evidence on comparative efficacy and safety.

CONCLUSION

This study will provide fundamental data for prospective research on the application of TEAM in patients with obesity.

PROTOCOL REGISTRY NUMBER OF ONLINE REGISTRY

This study protocol was registered in open Science framework (OSF) (Registration DOI: 10.17605/OSF.IO/ETWDS).

URL OF THE ONLINE REGISTRY

https://osf.io/etwds.

Phytochemistry profile of rosella and jambolan extracts and the therapeutic effects on obesity

Hibiscus sabdariffa extract (HSE) and Syzygium cumini extract (SCE) have been used in traditional medicine due to their hypoglycemic, antidiabetic, anti-obesity and antioxidant activities. The aim of this study was...

Medicinal Plants and Their Inhibitory Activities against Pancreatic Lipase: A Review

Obesity is recognized as a major life style disorder especially in developing countries and it is prevailing at an alarming speed in new world countries due to fast food intake, industrialization, and reduction of physical activity. Furthermore, it is associated with a vast number of chronic diseases and disabilities. To date, relatively effective drugs, from either natural or synthetic sources, are generally associated with serious side effects, often leading to cessation of clinical trials or even withdrawal from the market. In order to find new compounds which are more effective or with less adverse effects compared to orlistat, the drug that has been approved for obesity, new compounds isolated from natural products are being identified and screened for antiobesity effects, in particular, for their pancreatic lipase inhibitory effect. Pancreatic lipase inhibitory activity has been extensively used for the determination of potential efficacy of natural products as antiobesity agents. In attempts to identify natural products for overcoming obesity, more researches have been focused on the identification of newer pancreatic lipase inhibitors with less unpleasant adverse effects. In this review, we consider the potential role of plants that have been investigated for their pancreatic lipase inhibitory activity.

Safety of antiobesity drugs

Obesity is a major health problem worldwide. Although diet and physical activity are crucial in the management of obesity, the long-term success rate is low. Therefore antiobesity drugs are of great interest, especially when lifestyle modification has failed. As obesity is not an immediate life-threatening disease, these drugs are required to be safe. Antiobesity drugs that have been developed so far have limited efficacies and considerable adverse effects affecting tolerability and safety. Therefore, most antiobesity drugs have been withdrawn. Fenfluramine and dexfenfluramine were withdrawn because of the potential damage to heart valves. Sibutramine was associated with an increase in major adverse cardiovascular events in the Sibutramine Cardiovascular Outcomes (SCOUT) trial and it was withdrawn from the market in 2010. Rimonabant was withdrawn because of significant psychiatric adverse effects. Orlistat was approved in Europe and the United States for long-term treatment of obesity, but many patients cannot tolerate its gastrointestinal side effects. Phentermine and diethylpropion can only be used for less than 12 weeks because the long-term safety of these drugs is unknown. Ephedrine and caffeine are natural substances but the effects on weight reduction are modest. As a result there is a huge unmet need for effective and safe antiobesity drugs. Recently lorcaserin and topiramate plus phentermine have been approved for the treatment of obesity but long-term safety data are lacking.

Combination of very low energy diets and pharmacotherapy in the treatment of obesity: meta-analysis of published data

Obesity has reached epidemic proportions globally, with more than 1 billion adults overweight - at least 300 million of them clinically obese - and is a major contributor to the global burden of chronic disease (heart disease and diabetes) and disability. The aim of the study was to perform a systematic review and meta-analysis of published data on the combination of very low energy diets also known as very low calorie diets and pharmacotherapy for its effectiveness in the treatment of obesity. A MEDLINE (Pubmed) search from 1970 to 2009 using multiple combinations of the relevant terms was carried out; the matching articles were also searched for additional references. Meta-analysis tools were used to summarize results. Only randomized controlled trials that compared pharmacotherapy with placebo after a very low energy diet period were selected, and six articles were finally considered to be appropriate for evaluation. The combination of very low energy diet and pharmacotherapy was found to be effective for people with obesity in clinical trials. The net effect of 6.1 kg placebo subtracted weight loss after 1 year represents a clinically meaningful result that is comparable with the effect of drugs given at the start of a weight loss programme. The present meta-analysis contributes to the understanding that combination therapies are expected to achieve greater weight loss than monotherapy; grasping this understanding, researcher has introduced newer anti-obesity pharmacological approaches have embraced combination therapies.

Changes in cardiovascular risk associated with phentermine and topiramate extended-release in participants with comorbidities and a body mass index ≥27 kg/m(2)

The aim of this analysis was to evaluate changes in cardiovascular risk factors in obese patients with dyslipidemia and/or hypertension receiving phentermine (PHEN) and topiramate extended-release (TPM ER). In the 56-week, randomized, double-blind, placebo-controlled, multicenter CONQUER trial, PHEN/TPM ER demonstrated significant weight loss compared with placebo in overweight or obese participants with ≥2 weight-related co-morbidities. Participants with body mass indexes of 27 to 45 kg/m(2) were randomized to placebo, PHEN 7.5 mg/TPM ER 46 mg, or PHEN 15 mg/TPM ER 92 mg; participants also received lifestyle modification counseling. Primary end points were percentage weight loss and the proportion of participants achieving ≥5% weight loss. Additional end points were changes in lipid variables in the dyslipidemia population and blood pressure in the hypertensive population, stratified by treatment and magnitude of weight loss. PHEN/TPM ER produced significantly greater dose-related mean percentage weight loss compared with placebo in the subgroups of participants with dyslipidemia and those with hypertension. Regardless of treatment group assignment, participants with dyslipidemia who lost ≥5% of their baseline weight experienced significantly greater reductions in triglycerides (-14.5% to -39.8%), and in non-high-density lipoprotein cholesterol (-9.4% to -14.8%) than those losing <5% of their weight (p <0.05). Similarly, participants with hypertension at baseline showed reduced systolic blood pressure by -7.5 to -11.8 mm Hg (p <0.001 vs those with <5% weight loss). In conclusion, the dose-related weight loss induced by PHEN/TPM ER treatment was accompanied by significant improvements in cardiovascular disease risk factors in participants who had dyslipidemia or hypertension at baseline, suggesting that facilitating weight loss by augmenting lifestyle changes with pharmacotherapies may decrease the risk for cardiovascular disease in obese and overweight patients with co-morbidities.

How safe is the use of herbal weight-loss products sold over the internet?

BACKGROUND

In recent years, the use of herbal weight-loss products sold over the Internet has rapidly increased; however, the safety of these products has not been well documented yet. More importantly, the declared ingredients in these products could be different than the marketed contents.

METHODS

Nine different herbal weight-loss products sold over the Internet were obtained. The ingredients of each product were analyzed in the Laboratory of Forensic Medicine and the Scientific and Technological Research Laboratory of Inonu University.

RESULTS

Although all studied weight-loss products were presented as pure herbal, three of them contain sibutramine, three contain caffeine, and three contain caffeine + temazepam. The amount of sibutramine in each capsule was found to be over 10 mg. We analyzed toxic and trace element levels of nine herbal products and found that these herbal products, even in low amounts, contain Pb, Al, Ni, and Ba.

CONCLUSIONS

Our results indicate that herbal weight-loss products available without prescription and claimed to be purely herbal may contain pharmaceutical substances like sibutramine or temazepam in high doses. Moreover, they also may become contaminated with toxic metals. Since people commonly use these products unaware of its real constituents and without the suggestion or control of a physician, they might cause various health problems some of which might be harmful. Strict legal rules and control mechanisms must be established to minimize their possible harmful effects.

Drug treatment for obesity in the post-sibutramine era

Obesity is a major health problem worldwide. It is associated with cardiovascular diseases, diabetes mellitus and decreased longevity. In managing obesity, diet and exercise are essential; pharmacological therapy may be added for obese patients or overweight patients with cardiovascular risk factors. Sibutramine is a serotonergic and adrenergic drug that reduces food intake and increases thermogenesis. It reduces bodyweight by about 4.2 kg after 12 months, and improves blood glucose and lipids; however, it can increase heart rate and blood pressure. In the SCOUT (Sibutramine Cardiovascular OUTcomes) study, sibutramine increased serious cardiovascular events, such as stroke or myocardial infarction, compared with placebo, and was consequently withdrawn from the market. The lesson learnt from this is the importance of patient selection, limiting the duration of treatment and stopping treatment in non-responders. Currently, phentermine and amfepramone (diethylpropion) are approved for short-term treatment of obesity (up to 3 months) and orlistat is approved for longer-term treatment; however, the gastrointestinal adverse effects of orlistat may be intolerable for some patients. There is now a clear need to find anti-obesity drugs that are effective and safe in the long term.

Absence of sibutramine effect on spontaneous anxiety in rats

INTRODUSTION: Sibutramine has been described as a drug recommended for treatment of obesity, since it has the ability to inhibit the reuptake of serotonin and noradrenaline in the central nervous system, thereby increasing energy expenditure.

OBJECTIVE

Investigate the anxiogenic and anxiolytic effects of acute and chronic treatment with sibutramine in rats submitted to the task of the elevated plus-maze.

METHODS

Diazepam was used as a positive control for the anxiolytic effect, and the task of the elevated plus-maze showed sensitivity to detect the effect. In the chronic treatment, sibutramine was ingested for a period of two months.

RESULTS

The acute and chronic treatments at the studied dose, which is described to produce a maximum effect of anti-obesity in rats, did not interfere with anxiety.

CONCLUSIONS

The acute and chronic administration of sibutramine is not related to anxiolytic or anxiogenic effects.

Rise and fall of anti-obesity drugs

Although it is not generally a life-threatening disease, obesity is becoming a major health problem worldwide. It can be controlled by means of drugs, and, consequently, these are required to be safe as well as effective. In this paper, we summarize the fate of various drugs that have been introduced for clinical use in the treatment of obesity. Fenfluramine and dexfenfluramine were withdrawn because of heart valve damage. Sibutramine suppresses appetite and increases heart rate and blood pressure. In the Sibutramine Cardiovascular OUTcomes trial, an increase in major adverse cardiovascular events prompted its withdrawal in Europe and the United States. Rimonabant is an endocannabinoid receptor antagonist that reduces body weight and ameliorates some cardiovascular risk factors. However, adverse psychiatric side effects led to its withdrawal as well. Orlistat is approved in Europe and the United States for the treatment of obesity, but its use is limited by gastrointestinal side-effects. Ephedrine and caffeine are natural ingredients in foods and supplements that may help the person to lose weight. In the light of several failed attempts, there is a clear need to develop drugs that are effective and safe in the long term in order to successfully combat the phenomenon of obesity .

Cardiovascular risk-benefit profile of sibutramine

Sibutramine is a combined norepinephrine and serotonin reuptake inhibitor used as an antiobesity agent to reduce appetite and promote weight loss in combination with diet and exercise. At a daily dose of 10-20 mg, it was initially considered to have a good safety profile, as it does not induce primary pulmonary hypertension or adverse effects on cardiac valves, in contrast to previous reports relating to some other antiobesity agents. However, it exerts disparate effects on cardiovascular risk factors. On the one hand, sibutramine may have antiatherogenic activities, as it improves insulin resistance, glucose metabolism, dyslipidemia, and inflammatory markers, with most of these effects resulting from weight loss rather than from an intrinsic effect of the drug. On the other hand, because of its specific mode of action, sibutramine exerts a peripheral sympathomimetic effect, which induces a moderate increase in heart rate and attenuates the reduction in BP attributable to weight loss or even slightly increases BP. It may also prolong the QT interval, an effect that could induce arrhythmias. Because of these complex effects, it is difficult to conclude what the final impact of sibutramine on cardiovascular outcomes might be. Sibutramine has been shown to exert favorable effects on some surrogate cardiovascular endpoints such as reduction of left ventricular hypertrophy and improvement of endothelial dysfunction. A good cardiovascular safety profile was demonstrated in numerous 1- to 2-year controlled trials, in both diabetic and nondiabetic well selected patients, as well as in several observational studies. However, since 2002, several cardiovascular adverse events (hypertension, tachycardia, arrhythmias, and myocardial infarction) have been reported in sibutramine-treated patients. This led to a contraindication of the use of this antiobesity agent in patients with established coronary heart disease, previous stroke, heart failure, or cardiac arrhythmias. SCOUT (Sibutramine Cardiovascular and Diabetes Outcome Study) was designed to prospectively evaluate the efficacy/safety ratio of sibutramine in a high-risk population. The efficacy/safety results of the first 6-week lead-in open period of treatment with sibutramine 10 mg/day were reassuring in 10 742 overweight/obese high-risk subjects (97% had cardiovascular disease, 88% had hypertension, and 84% had type 2 diabetes mellitus). However, the final results of SCOUT showed that long-term (5 years') treatment with sibutramine (10-15 mg/day) exposed subjects with pre-existing cardiovascular disease to a significantly increased risk for nonfatal myocardial infarction and nonfatal stroke, but not cardiovascular death or all-cause mortality. Because the benefit of sibutramine as a weight-loss aid seems not to outweigh the cardiovascular risks, the European Medicines Agency recommended the suspension of marketing authorizations for sibutramine across the EU. The US FDA stated that the drug should carry a 'black box' warning due to an increased risk of stroke and heart attack in patients with a history of cardiovascular disease. In conclusion, concern still persists about the safety profile of sibutramine regarding cardiovascular outcomes, and the drug should not be prescribed for overweight/obese patients with a high cardiovascular risk profile.

Comparison of rimonabant and sibutramine treatment effects on food compulsion in rats

PURPOSE: To compare the therapeutic effect of rimonabant, a new drug which is a selective antagonist of CB1 receptors, with the sibutramine. METHODS: It is an experimental clinical trial, prospective, placebo controlled. Our test was performed in 38 rats, adults females with a hyper caloric diet. We collected their blood 3 times and weighted them once a week. We divided the rats in 3 groups: Rimonabant, Sibutramine and Control. Statistic analysis has been made through ANOVA test, Tukey test and t Student test. RESULTS: The Rimonabant group demonstrated a significant reduction of the weight increase in rats. The Sibutramine group showed a significant reduction on blood glycemia compared to Rimonabant group and Control group. CONCLUSIONS: Rimonabant showed to be more effective than Sibutramine by decreasing weight gain. Sibutramine has been more effective than Rimonabant and Control groups by decreasing the blood glycemia.

Review paper: Current strategies in the development of anti-obesity drugs and their safety concerns

Obesity is a well-established risk factor for hypertension, hyperlipidemia, type II diabetes, coronary heart disease, stroke, obstructive sleep apnea, asthma, orthopedic disorders, and certain cancers. Despite this risk, the prevalence of obesity continues to increase worldwide, and there is a growing demand for safe and effective antiobesity drugs. Previous antiobesity drugs or anorexigens, particularly centrally acting agents, have poor safety records. Life-threatening safety issues led to the withdrawal of aminorex in 1968, fenfluramine and dexfenfluramine in 1997, and phenylpropanolamine in 2000. Many of the safety issues, such as valvulopathy with fenfluramine and pulmonary arterial hypertension with aminorex, were initially not predicted by routine preclinical toxicology studies. To date, there are no validated animal models or preclinical and/or toxicologic screens to accurately predict anorexigen-induced valvulopathy and pulmonary arterial hypertension in humans. This review covers the current state of antiobesity drugs and their safety concerns, and highlights new therapeutic targets and scientific advances toward the development of appropriate animal models by using novel techniques that will aid in understanding pathogenesis and pathophysiology of anorexigen-related safety issues.

Nutritional supplements cross-contaminated and faked with doping substances

Since 1999 several groups have analyzed nutritional supplements with mass spectrometric methods (GC/MS, LC/MS/MS) for contaminations and adulterations with doping substances. These investigations showed that nutritional supplements contained prohibited stimulants as ephedrines, caffeine, methylenedioxymetamphetamie and sibutramine, which were not declared on the labels. An international study performed in 2001 and 2002 on 634 nutritional supplements that were purchased in 13 different countries showed that about 15% of the nonhormonal nutritional supplements were contaminated with anabolic-androgenic steroids (mainly prohormones). Since 2002, also products intentionally faked with high amounts of 'classic' anabolic steroids such as metandienone, stanozolol, boldenone, dehydrochloromethyl-testosterone, oxandrolone etc. have been detected on the nutritional supplement market. These anabolic steroids were not declared on the labels either. The sources of these anabolic steroids are probably Chinese pharmaceutical companies, which sell bulk material of anabolic steroids. In 2005 vitamin C, multivitamin and magnesium tablets were confiscated, which contained cross-contaminations of stanozolol and metandienone. Since 2002 new 'designer' steroids such as prostanozol, methasterone, androstatrienedione etc. have been offered on the nutritional supplement market. In the near future also cross-contaminations with these steroids are expected. Recently a nutritional supplement for weight loss was found to contain the beta2-agonist clenbuterol. The application of such nutritional supplements is connected with a high risk of inadvertent doping cases and a health risk. For the detection of new 'designer' steroids in nutritional supplements, mass spectrometric strategies (GC/MS, LC/MS/MS) are presented.

A novel promoter polymorphism in the human gene GNAS affects binding of transcription factor upstream stimulatory factor 1, Galphas protein expression and body weight regulation

OBJECTIVES

Body weight regulation is under complex control involving the central nervous system and peripheral pathways. The beta-adrenoceptor Galphas protein system plays an important role in heart rate regulation and lipid mobilization suggesting a key role for the stimulatory G protein Galphas in body weight regulation.

METHODS

We sequenced the whole GNAS promoter to identify a functional variant which results in altered Galphas expression. We genotyped 110 participants of a randomized placebo-controlled weight loss trial who were under a low calorie diet and were additionally treated with either placebo or 15 mg sibutramine daily for 54 weeks and associated the respective alleles with regard to treatment outcome using an intention-to-treat analysis.

RESULTS

A G>A transition at position -1211 the human GNAS promoter (minor allele frequency=0.36) was identified resulting in altered upstream stimulatory factor 1 transcription factor binding, promoter activity, Galphas expression, and lipolysis. Under a low calorie diet -1211GG genotypes lost significantly more weight compared with A-allele carriers (placebo group: 1211GG, 7.5+/-0.4 versus -1211A, 4.5+/-0.3 kg, P=0.020). Sibutramine was effective only in A-allele carriers whereas GG genotypes showed no additional weight loss under sibutramine but showed the strongest increases in resting heart rate (8.5 bpm; 95% confidence interval: 2.7-14.21 bpm; P=0.005) and systolic blood pressure (9.1 mmHg, 95% confidence interval: 3.1-15.1; P=0.004) compared with placebo.

CONCLUSIONS

Determination of GNAS promoter alleles may identify obese individuals who lose weight easily under lifestyle changes alone but also those who benefit from adjunct sibutramine therapy.

Sibutramine usage in New Zealand: an analysis of prescription data by the Intensive Medicines Monitoring Programme

PURPOSE

To describe patterns of sibutramine usage in New Zealand during the first 3 years of marketing using data acquired during post-marketing safety surveillance.

METHODS

Demographic and prescription data were examined from a nationwide cohort of 17 298 patients prescribed sibutramine between 1 February 2001 and 31 March 2004. Outcome measures were age and sex distribution of the cohort; period prevalence of sibutramine usage for each ethnic group; duration of treatment and reasons for cessation of therapy. Limited BMI data were also examined.

RESULTS

About 0.5% of the NZ population were prescribed sibutramine in the period studied. Overwhelmingly, the highest users of sibutramine were NZ European women aged 30-59 years. Maori and Pacific Peoples were under-represented in the cohort, despite the higher prevalence of obesity among these populations. Sibutramine usage was predominantly short-term: 59% of the cohort used sibutramine for 90 days or less, half of whom used it for only 1 month.

CONCLUSIONS

There has been extensive use of sibutramine in New Zealand. Sibutramine has been relatively under-utilised by Maori and Pacific ethnic groups, compared to New Zealand Europeans, despite their higher prevalence of obesity. A number of factors may have contributed to the predominantly short-term use of this medicine, including the cost of the medicine to the consumer, weight loss not meeting expectations and adverse effects of the medicine.

Drug treatments for obesity: orlistat, sibutramine, and rimonabant

Antiobesity treatment is recommended for selected patients in whom lifestyle modification is unsuccessful. Two antiobesity drugs are currently licensed for long-term use. Orlistat, a gastrointestinal lipase inhibitor, reduces weight by around 3 kg on average and decreases progression to diabetes in high-risk patients; adverse gastrointestinal effects are common. Sibutramine, a monoamine-reuptake inhibitor, results in mean weight losses of 4-5 kg, but is associated with increases in blood pressure and pulse rate. Rimonabant, the first of the endocannabinoid receptor antagonists, reduces weight by 4-5 kg on average and improves waist circumference and concentrations of HDL cholesterol and triglyceride; however, an increased incidence of mood-related disorders has been reported. To date, all antiobesity drug trials have been limited by their high attrition rates and lack of long-term morbidity and mortality data. Other promising antiobesity drugs, including those acting within the central melanocortin pathway, are in development, but are years away from clinical use. In light of the lack of successful weight-loss treatments and the public-health implications of the obesity pandemic, the development of safe and effective drugs should be a priority. However, as new drugs are developed we suggest that the assessment processes should include both surrogate endpoints (ie, weight loss) and clinical outcomes (ie, major obesity-related morbidity and mortality). Only then can patients and their physicians be confident that the putative benefits of such drugs outweigh their risks and costs.

Impact of weight-loss medications on the cardiovascular system: focus on current and future anti-obesity drugs

Overweight and obesity have been rising dramatically worldwide and are associated with numerous co-morbidities such as cardiovascular disease (CVD), type 2 diabetes mellitus, hypertension, certain cancers, and sleep apnea. In fact, obesity is an independent risk factor for CVD and CVD risks have also been documented in obese children. The majority of overweight and obese patients who achieve a significant short-term weight loss do not maintain their lower bodyweight in the long term. This may be due to a lack of intensive counseling and support from a facilitating environment including dedicated healthcare professionals such as nutritionists, kinesiologists, and behavior specialists. As a result, there has been a considerable focus on the role of adjunctive therapy such as pharmacotherapy for long-term weight loss and weight maintenance. Beyond an unfavorable risk factor profile, overweight and obesity also impact upon heart structure and function. Since the beginning, the quest for weight loss drugs has encountered warnings from regulatory agencies and the withdrawal from the market of efficient but unsafe medications. Fenfluramine was withdrawn from the market because of unacceptable pulmonary and cardiac adverse effects. Nevertheless, there is extensive research directed at the development of new anti-obesity compounds. The effect of these molecules on CVD risk factors has been studied and reported but information regarding their impact on the cardiovascular system is sparse. Thus, instead of looking at the benefit of weight loss on metabolism and risk factor management, this article discusses the impact of weight loss medications on the cardiovascular system. The potential interaction of available and potential new weight loss drugs with heart function and structure is reviewed.

Locomotor and peripheral effects of sibutramine modulated by 5-HT2 receptors

Sibutramine has been described as an anti-obesity drug with the ability to inhibit serotonin (5-HT), noradrenaline, and dopamine re-uptake, but without affinity to histamine and muscarinic receptors. On the other hand, cyproheptadine antagonizes serotonin 5-HT2A, 5-HT2B, and 5-HT2C, histamine H1, and muscarinic (M) receptors. There are many reports concerning the influence of sibutramine on central serotoninergic pathways. In this study, we suggest that peripheral pathways may also be involved in the serotoninergic effects of sibutramine. In vivo experiments were undertaken to investigate the serotoninergic effects of sibutramine on body mass, the glycogen concentration in the diaphragm of rats, and locomotor behaviour. Rats were submitted to oral treatment with sibutramine, cyproheptadine, or sibutramine applied in combination with cyproheptadine, for a period of 2 months to investigate the 5-HT2 effects of sibutramine on these parameters. As the results demonstrated, the lower increase in body mass and the increased glycogen levels in the diaphragm muscle of rats treated with sibutramine seem to be modulated by 5-HT2 receptors, since these effects were completely antagonized by cyproheptadine in the group treated with the 2 drugs co-applied. Furthermore, the behavioural results also suggest that mechanisms modulated by 5-HT2 receptors are involved in the increase of locomotion in the rats treated with sibutramine, since the effect did not occur in the rats treated with sibutramine co-applied with the 5-HT2 receptor antagonist, cyproheptadine. The results suggest that sibutramine modifies energy-related parameters such as body mass, diaphragm glycogen, and locomotor behaviour in rats via 5-HT2 serotoninergic pathways.

Assessment of clinical and economic benefits of weight management with sibutramine in general practice in Germany

Obesity is associated with major health risks and a high economic burden impacting on health care systems. This study utilises the latest evidence from randomised clinical trials (RCTs) to explore and to assess the cost effectiveness of sibutramine in combination with diet and lifestyle advice compared to diet and lifestyle advice alone for the treatment of obese subjects without comorbidities at baseline in Germany. New evidence from recently published RCTs and post-marketing surveillance studies, including health economic data as well as quality of life (QoL) data, were used to model the long-term outcomes of weight management with sibutramine in German practice. German healthcare costs and new data from over 8,000 patients were analysed based on a recently published model. These new RCT data were used to model weight losses, proportion of responders to treatment, utilities by weight loss and variability in weight regain post-treatment. Costs and QoL benefits associated with weight loss (using SF-36 data from sibutramine trials), reduced incidence of coronary heart disease (using Framingham equations) and diabetes were used to estimate the cost per quality adjusted life year of sibutramine treatment. For 1,000 patients treated with sibutramine for 1 year, extrapolating outcomes over 4 further years, sibutramine is estimated to save 4.18 CHD events, 2.58 diabetes incident cases and give 51.5 more quality-adjusted life years (QALYs). The cost-utility analysis (CUA) estimates 13,706 euro per QALY gained. Results are sensitive to changes in weight loss, rate of weight regain and discounting rate. Although the non-pharmacological weight management programme in the comparator arm yielded higher weight losses than generally observed in clinical practice, these results demonstrate that additional sibutramine treatment is a cost effective therapy for an obese population without comorbidities in Germany. The CUA results are within the range generally accepted as cost effective and should be viewed as conservative when generalizing to settings offering standard non-pharmacological treatment.

Safety of drug therapies used for weight loss and treatment of obesity

Some of the medications used for weight loss in the management of obesity have been associated with unacceptable morbidity and mortality. Safety concerns have led to the withdrawal of aminorex, followed by the fenfluramines in 1997, and phenylpropanolamine (norephedrine) in 2000. Aminorex was associated with an increased prevalence of primary pulmonary hypertension (PPH), fenfluramines with an increased prevalence of PPH and valvulopathy, and phenylpropanolamine with an increased risk of haemorrhagic stroke. Several studies have investigated the safety of the fenfluramines, yet the benefit-risk profile has not been conclusively quantified. This is due to several deficiencies in the published studies, including a lack of data on the baseline prevalences of comorbid conditions in obese subjects, and potential confounders and biases in the study designs. Although several studies and systematic reviews support an increased risk of PPH and valvulopathy in patients who have taken fenfluramines, without knowledge of the background prevalence it is not possible to determine if the exposure preceded the outcome. The population at higher risk of these adverse effects includes those taking higher doses or with a longer duration of exposure to fenfluramines and those with pre-existing cardiac disease or a genetic predisposition. Patients exposed to fenfluramines continue to be monitored, with some follow-up studies indicating no overall worsening in valvulopathy over time. There are limited efficacy and safety data for amfepramone (diethylpropion) and phentermine and their approval for the management of obesity is limited to short-term use. Orlistat and sibutramine are the only currently approved medications for long-term management of obesity. Although the benefit-risk profiles of sibutramine and orlistat appear positive, sibutramine continues to be monitored because of long-term safety concerns. The safety and efficacy of currently approved drug therapies have not been evaluated in children and elderly patient populations and there is limited information in adolescents, whilst the long-term safety of current and potential new drug therapies in adults will require several years of postmarketing surveillance to fully elucidate their adverse effect profiles.

An update on the pharmacological treatment of obesity

OBJECTIVE

To review the commonly utilized pharmacological options for the treatment of overweight and obese patients in the United States.

METHODS

A MEDLINE and EMBASE search, in English, between January 1995 and November 2005 was conducted using the terms, "anti-obesity agents", "orlistat", "sibutramine", and "phentermine". References cited in relevant studies and reviews were also examined for additional clinical trials to be included in the review.

RESULTS

There are several pharmacological options currently available for the treatment of overweight and obese individuals in the United States, including phentermine, sibutramine, and orlistat, with only sibutramine and orlistat being indicated for use in the long term (> 6 months). However, none of these medications have proven to be more effective than another for the indication of weight loss, each with a very similar maximum weight loss potential. Therefore choosing a weight loss medication should be patient specific and based on its pharmacological profile, including mechanism of action and potential adverse effects. Most importantly, it is imperative to realize that these agents are only indicated for use when combined with lifestyle modifications. Most studies have indicated that maximum benefits from any of these medications are only shown when taken in addition to a hypocaloric diet.

CONCLUSION

It has been shown that the combination of lifestyle changes and pharmacological treatment leads to a greater decrease in total body weight loss. Treatment with anti-obesity agents is associated with side effects and an increased cost in health care. These factors must be weighed prior to initiating anti-obesity treatment.

Pharmacotherapy for obesity

Pharmacotherapy for the management of obesity is primarily aimed at weight loss, weight loss maintenance and risk reduction, and has included thyroid hormone, amphetamines, phentermine, amfepramone (diethylpropion), phenylpropanolamine, mazindol, fenfluramines and, more recently, sibutramine and orlistat. These agents decrease appetite, reduce absorption of fat or increase energy expenditure. Primary endpoints used to evaluate anti-obesity drugs most frequently include mean weight loss, percentage weight loss and proportion of patients losing >or=5% and >or=10% of initial bodyweight. Secondary endpoints may include reduction in body fat, risk factors for cardiovascular disease and the incidences of diseases such as diabetes mellitus. Most pharmacotherapies have demonstrated significantly greater weight loss in patients on active treatment than those receiving placebo in short-term (<or=1 year) randomised controlled trials of pharmacological treatment in conjunction with a calorie-controlled diet or lifestyle intervention. The evidence of long-term efficacy is limited to sibutramine (2 years) and orlistat (4 years). These are the only drugs currently approved for the long-term management of obesity in adults. Sibutramine recipients randomised following 6 months' treatment to either sibutramine or placebo demonstrated significantly better weight maintenance at 2 years than those taking placebo (p<0.001), with >or=10% loss of initial bodyweight in 46% of patients. For patients taking orlistat, weight loss was 2.2 kg greater than those on placebo at 4 years (p<0.001), with significantly more patients achieving >or=10% loss of initial bodyweight (26.2% and 15.6%, respectively; p<0.001). Other drugs that have been evaluated for weight loss include ephedrine, the antidepressants fluoxetine and bupropion, and the antiepileptics topiramate and zonisamide. Two clinical trials with fluoxetine both reported no significant difference in weight loss compared with placebo at 52 weeks. Clinical trials evaluating ephedrine, bupropion, topiramate and zonisamide have demonstrated significantly greater weight loss than placebo but have been limited to 16-26 weeks' treatment. A major obstacle to the evaluation of the clinical trials is the potential bias resulting from low study completion rates. Completion rates varied from 52.8% of phentermine recipients in a 9-month study, to 40% of fenfluramine recipients in a 24-week comparative study with phentermine and 18% of amfepramone recipients in a 24-week study. One-year completion rates range from 51% to 73% for sibutramine and from 66% to 85% for orlistat. Other potential sources of bias include run-in periods and subsequent patient selection based on compliance or initial weight loss. Several potential new therapies targeting weight loss and obesity through the CNS pathways or peripheral adiposity signals are in early phase clinical trials. Over the next decade the drug treatment of obesity is likely to change significantly because of the availability of new pharmacotherapies to regulate eating behaviours, nutrient partitioning and/or energy expenditure.

Safety of obesity drugs

The safety of obesity drugs has historically been poor. This and the stigmatisation of obesity in society ensured that a higher standard of safety for obesity drugs must be met. The authors review the safety disasters of obesity drugs that were withdrawn. The authors then review the safety of presently available drugs--benzphetamine, phendimetrazine, diethylpropion, phentermine, sibutramine and orlistat. The safety of rimonabant, a drug with a pending new drug application that has an independent effect on metabolic syndrome, is also reviewed. The authors compare the stage of obesity drug development to that of hypertension in the 1950s. As new and safer drugs with more downstream mechanisms are developed that have independent effects on the cardiovascular risks associated with obesity, third party reimbursement for obesity medicine is likely to improve. This may lead to obesity being treated like hypertension and other chronic diseases with long-term medication. With improved technological tools, the authors believe this process will be more rapid for obesity than it was for hypertension.

Neuropeptide Y, alpha-melanocyte-stimulating hormone, and monoamines in food intake regulation

Obesity is increasing in severity and prevalence in the United States and represents a major public health issue. No effective pharmacologic treatment leading to sustained weight loss currently exists. The growing interest in the regulation of food intake stems from the current drug treatments for obesity, almost all of which interfere with the monoamine system. Our knowledge of potential interactions between the orexigenic and anorexigenic pathways is limited and fragmented, making the development of targeted drug therapy for obesity difficult. The present review of the interaction of neuropeptides and monoamines emphasizes the complexity of the central mechanisms that regulate feeding behavior. Two main systems are implicated in food intake regulation: neuropeptide Y (NPY) and pro-opiomelanocortin. alpha-Melanocyte-stimulating hormone is a tridecapeptide cleaved from pro-opiomelanocortin that acts to inhibit food intake. The predominant NPY orexigenic receptors are NPY-Y1 and NPY-Y5, and the two anorexigenic melanocortin receptors involved in hypothalamic food intake control are MC3-R and MC4-R. Both neuropeptides interact with monoamines in the hypothalamus to control physiologic states such as hunger, satiation, and satiety. Serotonin suppresses food intake and body weight, acting mainly through the serotonin 1B receptor. Dopamine regulates hunger and satiety by acting in specific hypothalamic areas, through the D1 and D2 receptors. Noradrenaline activation of alpha1- and beta2-adrenoceptors decreases food intake, and stimulation of the alpha2-adrenoceptor increases food intake. A better understanding of the detailed mechanisms underlying the pathogenesis of hyperphagia and hypophagia is needed to develop new therapeutic approaches to obesity.

A review of the metabolic effects of sibutramine

BACKGROUND

Obesity is associated with an increased incidence of diabetes, hypertension, dyslipidaemia and coronary artery disease. Current management strategies of obesity include lifestyle management strategies of obesity include lifestyle interventions and pharmaco therapy. Sibutramine is a drug with established efficacy in weight reduction and maintenance of weight loss. It reduces food intake and attenuates the fall in reduces food intake and attenuates the fall in metabolic rate associated with weight loss.

OBJECTIVE

To review the metabolic effects associated with sibutramine use.

METHODS

Relevant articles were identified through a Medline search (up to December 2004).

RESULTS

Weight loss with sibutramine treatment is associated with improved insulin sensitivity and a fall in glycosylated haemoglobin levels in type 2 diabetic patients. In most trials sibutramine exerted favourable effects on lipids, especially exerted favourable effects on lipids, especially on high density lipoprotein (HDL) cholesterol and triglycerides, as well as on the total:HDL cholesterol ratio. Sibutramine also lowers serum uric acid concentrations. Furthermore, this drug seems to favourably influence adipocytokines; it reduces serum leptin and resistin levels and increases adiponectin levels. Sibutramine also exerts a beneficial effect on hyper androgenaemia in obese women with polycystic ovary syndrome. Preliminary findings also suggest that weight loss following treatment with sibutramine is useful in patients with non-alcoholic fatty liver disease (NAFLD).

CONCLUSION

Weight loss following sibutramine administration is associated with several favourable metabolic effects.

Emerging aspects of pharmacotherapy for obesity and metabolic syndrome

Obesity is a multifactorial, chronic disorder that has reached epidemic proportions in most industrialized countries and is threatening to become a global epidemic. Obese patients are at higher risk from coronary artery disease, hypertension, hyperlipidemia, diabetes mellitus, cancers, cerebrovascular accidents, osteoarthritis, restrictive pulmonary disease, and sleep apnoea. In particular, visceral fat accumulation is usually accompanied by insulin resistance or type 2 diabetes mellitus, hypertension, hypertriglyceridemia, high uremic acid levels, low high density lipoprotein (HDL) cholesterol to define a variously named syndrome or metabolic syndrome. Metabolic syndrome is now considered a major cardiovascular risk factor in a large percentage of population in worldwide. Both obesity and metabolic syndrome are particularly challenging clinical conditions to treat because of their complex pathophysiological basis. Indeed, body weight represents the integration of many biological and environmental components and relationships among fat and glucose tolerance or blood pressure are not completely understood. Efforts to develop innovative anti-obesity drugs, with benefits for metabolic syndrome, have been recently intensified. In general two distinct strategies can be adopted: first, to reduce energy intake; second, to increase energy expenditure. Here we review some among the most promising avenues in these two fields of drug therapy of obesity and, consequently, of metabolic syndrome.