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Concerns over whether the tests a treatment undergoes before release onto the market are enough to ensure its long-term safety are raised in an editorial published by BMJ Clinical Evidence today.
Dr Vijay Sharma suggests that treatments should be introduced gradually so that evidence can be built up and the treatment can find its proper niche.
To illustrate this, he discusses the recent debate on the long-term safety of drug-eluting stents. Stents (small tubes) are used to unblock arteries that have become thickened by fatty deposits. They improve blood flow and reduce the risk of death from coronary artery disease. Drug-eluting stents slowly release drugs to stop blood clots blocking the stented arteries, a process called restenosis.
Drug-eluting stents were used with great enthusiasm when first introduced in 2002, but since 2006 several reports have highlighted an increased risk of clotting as late as one year after treatment (known as late-stent thrombosis).
But why was this risk not detected sooner, asks the author?
One reason may relate to the outcomes that early clinical trials set out to measure. Another may be that trials have predominantly focused on low risk cases, yet drug-eluting stents were also used in complex cases, where the underlying risk of clotting is higher. More complex cases also require the use of more stents and longer stents, further increasing the risk of late-stent thrombosis, he explains.
All adverse effects must be carefully assessed in large-scale studies, writes Dr Sharma. But they must also be balanced against the threat posed by coronary artery disease itself, and interpreted in the context of other treatment options.
He concludes: “Treatments are often greeted with enthusiasm when they first appear only to fall into disfavour when adverse effects are found. Then, with time, some of these treatments return with a more limited and clearly defined use. To avoid this pattern, adverse effects should be actively sought, and treatments should be introduced gradually so that experience and evidence can be built up and the treatment can find its proper niche.”