Efficacy and safety of sibutramine in 2225 subjects with cardiovascular risk factors: short-term, open-label, observational study

The effectiveness of pharmaceutical interventions for obesity: weight loss with orlistat and sibutramine in a United Kingdom population-based cohort

Aims

Drug treatments for obesity have proven efficacy from randomized trials, but their effectiveness in routine clinical practice is unknown. We assessed the effects on weight and body mass index (BMI) of orlistat and sibutramine when delivered in routine primary care.

Methods

We used United Kingdom data from the Clinical Practice Research Datalink to estimate the effects of orlistat or sibutramine on weight and BMI over 3 years following treatment initiation. For comparison, we matched each patient with up to five obese patients receiving neither drug. Mixed effects linear regression with splines was used to model change in weight and BMI. Mean change with 95% confidence intervals (CI) was estimated.

Results

We identified 100 701 patients receiving orlistat, 15 355 receiving sibutramine and 508 140 non-intervention patients, with body mass index of 37.2, 36.6 and 33.2 kg m⁻², respectively. Patients receiving orlistat lost, on average, 0.94 kg month⁻¹ (0.93 to 0.95) over the first 4 months. Weight gain then occurred, although weight remained slightly below baseline at 3 years. Patients receiving sibutramine lost, 1.28 kg month⁻¹ (1.26 to 1.30) over the first 4 months, but by 3 years had exceeded baseline weight. Non-intervention patients had slight increases in weight throughout the 3 year period, with gains ranging between 0.01 and 0.06 kg month⁻¹.

Conclusions

Orlistat and sibutramine had early effects on weight loss, not sustained over 3 years. As new treatments for obesity are approved, their effectiveness should be measured in routine clinical practice, as effectiveness may be considerably less than seen in randomized trials.

Serotonin and blood pressure regulation

5-Hydroxytryptamine (5-HT; serotonin) was discovered more than 60 years ago as a substance isolated from blood. The neural effects of 5-HT have been well investigated and understood, thanks in part to the pharmacological tools available to dissect the serotonergic system and the development of the frequently prescribed selective serotonin-reuptake inhibitors. By contrast, our understanding of the role of 5-HT in the control and modification of blood pressure pales in comparison. Here we focus on the role of 5-HT in systemic blood pressure control. This review provides an in-depth study of the function and pharmacology of 5-HT in those tissues that can modify blood pressure (blood, vasculature, heart, adrenal gland, kidney, brain), with a focus on the autonomic nervous system that includes mechanisms of action and pharmacology of 5-HT within each system. We compare the change in blood pressure produced in different species by short- and long-term administration of 5-HT or selective serotonin receptor agonists. To further our understanding of the mechanisms through which 5-HT modifies blood pressure, we also describe the blood pressure effects of commonly used drugs that modify the actions of 5-HT. The pharmacology and physiological actions of 5-HT in modifying blood pressure are important, given its involvement in circulatory shock, orthostatic hypotension, serotonin syndrome and hypertension.

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.

Drugs in the treatment of obesity: sibutramine, orlistat and rimonabant

Background

Modification of lifestyle is the main therapeutical approach in the treatment of obesity, but use to fail on long terms of time. Addition of anti-obesity drugs allows keeping the weight loss during years and improving obesity-related comorbidities.

Methods

This review is an actualisation on efficacy, safety and tolerability of the approved drugs on the long-term treatment of obesity (orlistat and sibutramine). New indications and effects of their use far beyond the weight loss are as well commented. Finally, potential benefits of the administration of CB1 antagonist rimonabant on the weight loss and cardiometabolic risk factors are analysed in detail.

Discussion

A decade of experience on the use of orlistat and sibutramine has demonstrated their higher efficacy on the weight loss when compared to placebo either on adult or teenage population as well as safety and tolerability on long-term administration. Beneficial effects on the lipid profile, glycosilated haemoglobin on diabetic patients, blood pressure and levels of inflammatory cytokines, contribute to decrease the cardiovascular risk on obese patients. Phase III clinical trials using rimonabant show additional benefits to the expected weight loss, mainly reducing visceral fat and cardiometabolic risk factors.

Conclusion

Pharmacological treatment of obesity must be considered as a therapeutical tool that has to be used together with long-term lifestyle changes, contributing to the body weight reduction as well as to the improvement of the cardiometabolic risk related to obesity.

Metabolic syndrome: pathogenesis, medical care and dental implications

BACKGROUND

The dental literature contains little information about metabolic syndrome (MetS) and its dental implications.

TYPES OF STUDIES REVIEWED

The authors conducted a MEDLINE search for the period 2000 through 2005, using the term "metabolic syndrome" to define its pathophysiology, medical treatment and dental implications.

RESULTS

MetS is the co-occurrence of abdominal obesity, hyper-triglyceridemia, reduced high-density lipoprotein cholesterol levels, hypertension and impaired fasting glucose, which results from consumption of a high-calorie diet and decreased levels of physical activity superimposed on the appropriate genetic setting. Components of MetS synergistically promote the development of atherosclerosis, resulting in myocardial infarction and stroke.

CLINICAL IMPLICATIONS

Deteriorating oral health status is associated with worsening of the atherogenic profile. Tooth loss often results in chewing difficulties because of inadequate occlusive surfaces and may lead to alterations in food selection and dietary quality. This, in turn, adversely affects body composition and nutritional status, both of which are related to vascular health. Dentists should develop treatment plans that preserve and restore the dentition, thus ensuring maximum masticatory efficiency and affording patients the optimum opportunity to consume food that will not foster atherogenesis.

Neurochemical, neuroautonomic and neuropharmacological acute effects of sibutramine in healthy subjects

Sibutramine is a neuropharmacological drug that exerts central (CNS) and peripheral effects including noradrenaline (NA), and serotonin (5-HT) uptake inhibition. In addition, the drug is able to induce release from DA axons. We measured levels of circulating neurotransmitters in 20 healthy subjects during supine-resting (fasting) state before and after 15 mg of oral sibutramine. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were also monitored. Sibutramine triggered sustained and progressive increase of NA, NA/Ad ratio and DBP. Slight increases of DA were also registered between the 60 and 240 min periods. The rise in DA tended to fade progressively, reaching basal level at 360 min period. Diastolic blood pressure, but neither SBP nor HR, showed significant increases that correlated positively with NA/Ad ratios. Slight but significant negative correlation was also found between DBP and DA. This correlation tended to fade throughout the trial to show no significance at the 360 min period. Although neither plasma serotonin (f-5HT) nor platelet serotonin (p-5HT) values showed significant variation throughout the trial, the f-5HT/p-5HT ratio showed significant decrease throughout. Significant negative correlation was found between f-5HT/p-5HT ratio and NA/Ad ratio. Our results indicate that sibutramine stimulates neural sympathetic activity but not adrenal sympathetic activity in healthy individuals. Further, sibutramine lowers parasympathetic activity. The moderate rise in diastolic blood pressure triggered by sibutramine would be associated with CNS-NA enhancement plus parasympathetic inhibition.

Long-term pharmacotherapy for obesity and overweight

BACKGROUND

Worldwide prevalence rates of obesity and overweight are rising and safe and effective treatment strategies are urgently needed. A number of anti-obesity agents have been studied in short-term clinical trials, but long-term efficacy and safety need to be established.

OBJECTIVES

To assess/compare the effects and safety of approved anti-obesity medications in clinical trials of at least one-year duration.

SEARCH STRATEGY

MEDLINE, EMBASE, the Cochrane Controlled Trials Register, the Current Science Meta-register of Controlled Trials, and reference lists of original studies and reviews were searched. Date of last search was December 2002. Drug manufacturers and two obesity experts were contacted in to detect unpublished trials. No language restrictions were imposed.

SELECTION CRITERIA

Double-blind, randomised controlled weight loss and weight maintenance trials of approved anti-obesity agents that 1) enrolled adult overweight or obese patients, 2) included a placebo control group or compared two or more anti-obesity drugs 3) used an intention-to-treat analysis, and 4) had a minimum follow-up period of one year. Abstracts and pseudo-randomised trials were not included.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed all potentially relevant citations for inclusion and methodological quality. The primary outcome measure was weight loss.

MAIN RESULTS

Of the eight anti-obesity agents investigated, only orlistat and sibutramine trials met inclusion criteria. Eleven orlistat weight loss studies (four of which reported a second year weight maintenance phase) and five sibutramine studies (three weight loss and two weight maintenance trials) were included. Attrition rates averaged 33% during the weight loss phase of orlistat trials and 43% in sibutramine studies. All patients received lifestyle modification as a co-intervention. Compared to placebo, orlistat-treated patients lost 2.7 kg (95% CI: 2.3 kg to 3.1 kg) or 2.9% (95% CI: 2.3 % to 3.4%) more weight and patients on sibutramine experienced 4.3 kg (95% CI: 3.6 kg to 4.9 kg) or 4.6% (95% CI: 3.8% to 5.4%) greater weight loss. The number of patients achieving ten percent or greater weight loss was 12% (95% CI: 8% to 16%) higher with orlistat and 15% (95% CI: 4% to 27%) higher with sibutramine therapy. Weight loss maintenance results were similar. Orlistat caused gastrointestinal side effects and sibutramine was associated with small increases in blood pressure and pulse rate.

REVIEWERS' CONCLUSIONS

Studies evaluating the long-term efficacy of anti-obesity agents are limited to orlistat and sibutramine. Both drugs appear modestly effective in promoting weight loss; however, interpretation is limited by high attrition rates. Longer and more methodologically rigorous studies of anti-obesity drugs that are powered to examine endpoints such as mortality and cardiovascular morbidity are required to fully evaluate any potential benefit of such agents.