Patients taking weight loss drug rimonabant risk depression and anxiety, claim Danish researchers in The Lancet.
They re-analysed the results of four double blind randomised controlled trials, which included more than 4000 patients taking either 20 mg daily of rimonabant or placebo for a year.
They found that those taking the drug had lost just under 5 kilos more than those taking the placebo, but they were also 40% more likely to have psychiatric side effects, including depression and anxiety.
This was despite the fact that depressed mood was an exclusion criterion for participation in the trials, say the authors.
Those taking the drug were 2.5 times more likely than those in the placebo group to stop treatment because of depression and mood disorders.
And they were three times more likely to stop taking the drug because of anxiety.
The patients were not monitored after they had stopped their treatment, and relapse is relatively common, say the authors.
But to keep the weight off and maintain the improved health profile, patients need to keep taking it for life, they say.
“As with other weight loss drugs, relapse is expected to occur soon after treatment has ended, and to achieve weight maintenance and maintain the improvement of cardiovascular and diabetes risk factors, the drug needs to be taken for life,” they write.
“Taken together with the recent US Food and Drug Administration finding of increased risk of suicide during treatment with rimonabant, we recommend increased alertness by physicians to these potentially severe psychiatric adverse reactions.”
In an accompanying editorial, Professors Philip Mitchell and Margaret Morris of the University of New South Wales, in Sydney warn: “This meta analysis raises major questions about the safety of rimonabant in obese people, who are already are already at an increased risk of depression.”
Meanwhile a BMJ study, published ahead of print, suggests that weight loss drugs only provide “modest” improvements, with many people failing to shed enough weight after taking them.
The Canadian researchers reviewed the evidence from 30 placebo controlled trials where adults took orbital, or sibutramine, or rimonabant for a year or longer.
The study found that, the three drugs, which are recommended for long term use, reduced weight by less than 5 kg, or less than 5% of total body weight. Orlistat reduced weight by 2.9 kg, sibutramine by 4.2 kg, and rimonabant by 4.7 kg.
NICE guidelines recommend anti-obesity drugs should be stopped if 5% of total body weight is not lost after three months.
There were high drop-out levels in all the trials. On average 30 to 40% of patients failed to complete the trial.
Failure to stick to the treatment could be a major factor limiting the effectiveness of weight loss drugs, they suggest.
In 2005 global sales of anti-obesity drugs reached an estimated US $1.2 billion.
And in an accompanying editorial, Professor Gareth Williams warns that moves to sell these drugs over the counter in Europe could be very damaging.
“Selling anti-obesity drugs over the counter will perpetuate the myth that obesity can be fixed simply by popping a pill and could further undermine the efforts to promote healthy living, which is the only long term escape from obesity,” he says.
Lancet 2007; 370: 1706-13.
BMJ 2007; doi: 10.1136/bmj.39385.413113.25