Strong placebo response thwarts painkiller trials

Strong placebo response thwarts painkiller trials | Nature News & Comment

Drug companies have a problem: they are finding it ever harder to get painkillers through clinical trials. But this isn’t necessarily because the drugs are getting worse. An extensive analysis of trial data has found that responses to sham treatments have become stronger over time, making it harder to prove a drug’s advantage over placebo.

Simply being in a US trial and receiving sham treatment now seems to relieve pain almost as effectively as many promising new drugs. Mogil thinks that as US trials get longer, larger and more expensive, they may be enhancing participants’ expectations of their effectiveness.  

Stronger placebo responses have already been reported for trials of antidepressants and antipsychotics, triggering debate over whether growing placebo effects are seen in pain trials too. To find out, Mogil and his colleagues examined 84 clinical trials of drugs for the treatment of chronic neuropathic pain (pain which affects the nervous system) published between 1990 and 2013.

Based on patients’ ratings of their pain, the effect of trialled drugs in relieving symptoms stayed the same over the 23-year period — but placebo responses rose.

In 1996, patients in clinical trials reported that drugs relieved their pain by 27% more than did a placebo. But by 2013, that gap had slipped to just 9%. The phenomenon is driven by 35 US trials; among trials in Europe, Asia and elsewhere, there was no significant change in placebo reponses.The analysis is in press in the journal Pain.

Only in America

This effect would explain why drug companies have trouble getting new painkillers through trials, notes neuroscientist Fabrizio Benedetti, who studies placebo responses at the University of Turin, Italy. Over the past ten years, he says, more than 90% of potential drugs for treatment of neuropathic and cancer pain have failed at advanced phases of clinical trials.

But the finding that placebo responses are rising only in the United States is the most surprising aspect of the latest analysis.

One possible explanation is that direct-to-consumer advertising for drugs — allowed only in the United States and New Zealand — has increased people’s expectations of the benefits of drugs, creating stronger placebo effects.

But Mogil’s results hint at another factor. “Our data suggest that the longer a trial is and the bigger a trial is, the bigger the placebo is going to be,” he says.

Longer, bigger US trials probably cost more, and the glamour and gloss of their presentation might indirectly enhance patients’ expectations, Mogil speculates.

Some larger US trials also use contract research organizations that can employ nurses who are dedicated to the trial patients, he adds — giving patients a very different experience compared to those who take part in a small trial run by an academic lab, for instance, where research nurses may have many other responsibilities.

Mogil’s data also challenge one of the fundamental principles of placebo-controlled trials — that comparing a drug against placebo tells us how well a drug works.

A basic principle of these trials is that drug and placebo effects are additive: our total response to any drug we take is equal to the placebo response plus the drug’s biochemical effect. But Mogil found that although placebo responses have increased over time, drug responses haven’t risen by the same amount.

That suggests placebo and drug responses may not always be strictly additive. This isn’t entirely unexpected, Mogil argues, because both placebos and pharmaceutical painkillers tap into similar biological mechanisms — such as the release of endorphins in the brain.

But if true, it suggests that growing placebo responses are masking real painkilling effects. “There are a lot of people in the pain field who believe the drugs that are failing clinical trials actually work, it’s just that the trials can’t show it,” he says.

For companies trying to develop treatments, one remedy might be to compare new drugs against their best competitors instead of against placebo — or to go back to conducting smaller, shorter trials.

Mogil suggests it is also worth investigating the elements that generate the more powerful placebo response in US trials, and then incorporating those elements (such as the relationship between patient and nurse) into patient care.

Ted Kaptchuk, director of placebo research at Harvard Medical School in Boston, Massachusetts, agrees. “If the major component of a drug in any particular condition is its placebo component, we need to develop non-pharmacological interventions as a first-line response,” he says.  

Here’s another article on this problem with placebos.  Or is it a problem with Americans? After all, we are the only country that is showing this effect.

American placebo | Medical News Today

A new study finds that rising placebo responses may play a part in the increasingly high failure rate for clinical trials of drugs designed to control chronic pain caused by nerve damage. Surprisingly, however, the analysis of clinical trials conducted since 1990 found that the increase in placebo responses occurred only in trials conducted wholly in the U.S.; trials conducted in Europe or Asia showed no changes in placebo responses over that period.

researchers at McGill University in Montreal analyzed the results of 84 clinical trials of drugs conducted around the world from 1990 to 2013. Over that period, the pain inhibition experienced by patients in the placebo group increased steadily, reaching an average 30% decrease in pain levels by 2013

They found that in the U.S., but not elsewhere, trials are becoming longer (from an average of four-weeks long in 1990 to 12 weeks in 2013) and larger (from an average of fewer than 50 patients in 1990 to an average of more than 700 patients in 2013).

“The data suggest that longer and larger trials are associated with bigger placebo responses,”

“This, in turn, tends to result in the failure of those trials – since it makes it harder for pharmaceutical companies to prove that the drug being tested is more effective than treatment with a placebo.”

“It remains to be determined why the United States is an outlier with respect to its clinical trials,”

some potentially important differences between the U.S. and other countries. These include the existence of direct-to-consumer drug advertising in the U.S. (New Zealand is the only other country in the world that allows this), the greater spread of for-profit “contract research organizations” in the U.S., and perhaps greater exposure to the placebo concept in popular media in the U.S.

“The greater the improvement in patients treated with placebo in clinical trials, the more difficult it can be to demonstrate the beneficial effects of pain-relieving medications,”  



One thought on “Strong placebo response thwarts painkiller trials

  1. Payne Hertz

    My brother who used to live in Austin, Texas told me that a lot of his young friends who were desperate for money would volunteer for drug trials. There must have been a lot of such trials in Austin as I read that director Robert Rodriguez raised $7,000 to produce his first “Mariachi” movie by working as a guinea pig in clinical trials in Austin.

    He told me that most of these young people would just dump whatever meds they were given and tell the researchers whatever they thought they wanted to hear. They had no intention of risking their health and lives being guinea pigs. Considering they were as likely to ditch their placebo meds as the real drugs, it is not surprising the placebo response would be near identical to the drug response, since both were equally false.

    I wonder how common this kind of behavior is, and why I have never seen it mentioned in any discussion of the alleged superiority of the double-blind, placebo-controlled trial. There a lot of evidence that the results of these trials is often faked or manipulated on the research end, but no mention of the possibility they may be fake on the test subject end as well.

    Liked by 1 person


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