Clinical researchers should give more information about placebos – as sometimes they may be more active than described, according to an analysis published today.
Researchers at Oxford University cite several examples where placebos turned out to be active substances that affected the results of a clinical trial.
In one instance, early trials of lipid-lowering drugs used olive oils as a placebo – although the oil is thought to have a direct impact on cholesterol.
The analysis is published in the European Journal of Clinical Investigation.
They cite trials of oseltamivir, which used a placebo containing dehydrocholic acid to mimic the bitter taste of the drugs.
This substance can cause gastrointestinal symptoms – leading to the side-effects of the drug being under-reported.
The researchers examined 94 placebo-controlled trials and not one reported the ingredients used in the placebo.
Researcher Dr Jeremy Howick said: "There is a fundamental problem with this gold standard. Different placebos have very different effects, which then lead to, sometimes mistaken, inferences about a new treatment’s effects or harms.
"The idea that we need to report what’s in a placebo seems like overkill to many people because they mistakenly believe that placebos are inert, or white noise."
Fellow researcher Dr Rebecca Webster said: "It is impossible to say how often placebo components influence what the apparent benefit of the new treatment is until such components are reported adequately. As this study shows, they rarely are."
European Journal of Clinical Investigation 30 September 2019
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