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. Stronger placebo responses have [also] been reported for trials of antidepressants and antipsychotics.

The change in reponse to placebo treatments for pain, discovered by researchers in Canada, holds true only for US clinical trials. "We were absolutely floored when we found out," says Jeffrey Mogil, who directs the pain-genetics lab at McGill University in Montreal and led the analysis. Simply being in a US trial and receiving sham treatment now seems to relieve pain almost as effectively as many promising new drugs.

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.

Labels: Constants and Variables

¶ 5:16 AM