The New England Journal of Medicine has published the results of the SCOUT or Sibutramine Cardiovascular OUTcomes study. This study aimed to assess the effect of sibutramine (Reductil®) in individuals considered to be at high risk of a cardiovascular event. The results of this study led to the withdrawal of the drug in Europe in January 2010.
The study recruited 9,804 participants aged 55 years or older who were overweight or obese and had pre-existing cardiovascular disease, type 2 diabetes or both conditions. Participants went through a lead in period before treatment started, during this time average weight loss was 2.6kg, after which participants were randomised to treatment with placebo or 10-15mg of sibutramine. Follow up continued for a mean period of 3.4 years and during this time those on sibutramine maintained and added to this initial weight loss with an further loss of 1.7kg. However, there was an increased risk in the primary outcome which was a composite of nonfatal myocardial infarction, nonfatal stroke, resuscitation after cardiac arrest and cardiovascular death.
11.4% of the patients on the active treatment experienced the primary outcome compared to 10% of those on placebo (hazard ratio 1.16; 95% CI 1.03-1.31, p=0.02). This was mainly driven by increases in nonfatal myocardial (4.1% versus 3.2%, HR 1.28; 95% CI 1.04-1.57, p=0.02) and nonfatal stroke (2.6% versus 1.9%, HR 1.36; 95% CI 1.04-1.77, p=0.03).
Based on the absolute risk increase of 1.4% observed in the primary outcome, 71 patients would need to be treated for 3.4 years with sibutramine in order to see one additional cardiovascular event. This risk is balanced against a modest additional weight loss of 1.7kg.
The authors conclude that in patient with pre-existing cardiovascular conditions, "long-term sibutramine treatment had an increased risk of nonfatal myocardial infarction and nonfatal stroke".
Action: European authorities acted on the results of this trial back in January when the product license was suspended. Clinicians may find this data useful, if a little late, when quantifying risks to patients who took sibutramine.