Anti-Obesity Drugs Trial - Orlistat &
Sibutramine
Obesity Drugs Trial - 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.
Obesity Drugs Trial - Aim
To assess/compare the effects and safety of approved anti-obesity medications
in clinical trials of at least one-year duration.
Obesity Drugs Trial - Method
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unpublished trials.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.
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Obesity Drugs Trial - 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.
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Obesity Drugs Trial - Data Collection
and Analysis
Two reviewers independently assessed all potentially relevant citations
for inclusion and methodological quality. The primary outcome measure
was weight loss.
Obesity Drugs Trial - 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 percent during the
weight loss phase of orlistat trials and 43 percent in sibutramine studies.
All patients received lifestyle modification as a co-intervention. Compared
to placebo, orlistat-treated patients lost 2.7 kg or 2.9 percent more
weight and patients on sibutramine experienced 4.3 kg or 4.6 percent greater
weight loss. The number of patients achieving ten percent or greater weight
loss was 12 percent higher with orlistat and 15 percent 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.
Obesity Drugs Trial - 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.
Source: Padwal R, Li SK, Lau DCW. Long-term
pharmacotherapy for obesity and overweight (Cochrane Methodology Review).
In: The Cochrane Library, Issue 4, 2003.
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