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What is the Clinical Effectiveness and Cost-Effectiveness of Using Drugs in Treating Obese Patients in Primary Care? A Systematic Review

Health Technology Assessment, No. 16.5

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Author Information

,1,* ,1 ,2 ,1 ,2 ,2 ,2 ,1 ,1 ,1 ,2 ,2 ,2 ,2 and 2.

1 School of Health and Related Research (ScHARR), University of Sheffield, Sheffield, UK
2 Departments of Cardiovascular Sciences and Health Sciences, University of Leicester, Leicester, UK
* Corresponding author
Southampton (UK): NIHR Journals Library; .



Obesity [defined as a body mass index (BMI) ≥ 30 kg/m2] represents a considerable public health problem and is associated with a significant range of comorbidities and an increased mortality risk. The primary aim of the management of obesity is to achieve weight reduction in the interests of health. For obese patients who cannot achieve or maintain a healthy weight by non-pharmacological means, drug therapy is recommended in combination with non-pharmacological interventions such as dietary modifications and exercise.


To evaluate the clinical effectiveness and cost-effectiveness of three pharmacological interventions in obese patients.

Data sources:

Clinical effectiveness data used in the meta-analysis were sourced from articles identified in a systematic review of the literature. Data used to inform transitions to obesity-related comorbidities were derived from the General Practice Research Database (GPRD). The results of the meta-analysis and GPRD analyses informed the economic model supplemented by data from the Health Survey for England and other UK-specific data sourced from the literature.

Review methods:

A systematic literature review was conducted of the clinical effectiveness and cost-effectiveness of orlistat, sibutramine and rimonabant within their licensed indications for the treatment of obese patients. Electronic bibliographic databases including MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, EMBASE, The Cochrane Library databases and Cumulative Index to Nursing and Allied Health Literature (CINAHL) were searched in January 2009, and the reference lists of relevant articles were checked. Studies were included if they compared orlistat, sibutramine or rimonabant with lifestyle and/or exercise advice (standard care), placebo or metformin.


Overall, 94 studies involving 24,808 individuals were included in the clinical meta-analysis. Eighty-three trials included data on weight change, 41 included data on BMI change and 45 and 36 studies reported on 5% and 10% body weight loss, respectively. Overall, the results show that the active drug interventions are all effective at reducing weight and BMI compared with placebo. In the case of sibutramine, the higher dose (15 mg) resulted in a greater reduction than the lower dose (10 mg). Generally, the data quality of the trials included was low with poor reporting of standard errors and standard deviations. Results from the BMI risk models derived from the GPRD showed consistent increases in risk with increasing BMI. Adjustments for key confounders, such as age, sex and smoking status, were found to be statistically significant at the 5% level, in all risk models. Applying linear models to estimate BMI trajectories, for the diabetic cohort, an average increase in BMI of 0.040 per year for both men and women was observed. The non-diabetic cohort model showed an increase in BMI of 0.175 per year for women and 0.145 per year for men. The results of the cost-effectiveness analyses suggest that sibutramine 15 mg dominates the other three active interventions and the net benefit analyses show that sibutramine 15 mg is the most cost-effective alternative for thresholds > £2000 per quality-adjusted life-year (QALY). However, both sibutramine and rimonabant have been withdrawn because of safety concerns relating to potential treatment-induced fatal adverse events. If the proportion of patients who experienced a fatal adverse event was > 1.8% (1.5%, 1.0%) for sibutramine 15 mg (sibutramine 10 mg, rimonabant) the treatment would not be considered cost-effective when using a threshold of £20,000 per QALY.


The clinical review did not include all possible lifestyle comparators, with the inclusion limited to only those trials included one of the active drug interventions. We also excluded all studies not reported in English. Although the clinical review included data from 94 studies, the quality of data was generally low, particularly in terms of the reporting of standard deviation. There was also inconsistency between the results of the mixed-treatment comparison (MTC) and the pair-wise analyses.


The MTC of anti-obesity treatments shows that all the active treatments are effective at reducing weight and BMI. The economic results show that, compared with placebo, the treatments are all cost-effective when using a threshold of £20,000 per QALY, and, within the limitations of the data available, sibutramine 15 mg dominates the other three interventions. This work has highlighted many areas of methodological research that could be explored, including assessing inconsistencies within a network to determine differences between the results of pair-wise and MTC analyses; the use of meta-regression methods to look for effect modifiers; exploring the effect of local publication bias; and the use of joint models to analyse the repeated measures of BMI and the time-to-event processes simultaneously.


The National Institute for Health Research Health Technology Assessment programme.


Suggested citation:

Ara R, Blake L, Gray L, Hernández M, Crowther M, Dunkley A, et al. What is the clinical effectiveness and cost-effectiveness of using drugs in treating obese patients in primary care? A systematic review. Health Technol Assess 2012;16(5).

Declared competing interests of authors: KK has received funds for research or acted on advisory boards for Novartis, Novo Nordisk, Sanofi-Aventis, Eli Lilly and Merck Sharp & Dohme. He has received grants in support of investigator and investigator-initiated trials from Novartis, Novo Nordisk, Sanofi-Aventis, Eli Lilly, Pfizer, Boehringer Ingelheim and Merck Sharp & Dohme. MJD has received funds for research and honoraria for speaking at meetings and has served on advisory boards for Eli Lilly, Sanofi-Aventis, Merck Sharp & Dohme and Novo Nordisk.

The research reported in this issue of the journal was commissioned by the HTA programme as project number 07/85/02. The contractual start date was in January 2009. The draft report began editorial review in February 2011 and was accepted for publication in June 2011. As the funder, by devising a commissioning brief, the HTA programme specified the research question and study design. The authors have been wholly responsible for all data collection, analysis and interpretation, and for writing up their work. The HTA editors and publisher have tried to ensure the accuracy of the authors' report and would like to thank the referees for their constructive comments on the draft document. However, they do not accept liability for damages or losses arising from material published in this report.

The views expressed in this publication are those of the authors and not necessarily those of the HTA programme or the Department of Health.

© 2012, Crown Copyright.

Included under terms of UK Non-commercial Government License.

Bookshelf ID: NBK97589
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