A newly released study by Sunnybrook researchers has found that in industry-sponsored randomized controlled trials, antidepressants produced by a sponsor company are often dosed higher than nonsponsor comparator drugs. These findings suggest that comparative dose should be considered when interpreting results of sponsored trials.
"After examining the doses administered in 58 trials, we found that in 37% of those trials, the sponsor medication dose was higher, while in only 5% of trials, the nonsponsor medication dose was higher," says Dr. Mark Sinyor, Co-Chief Resident, Psychiatry, Sunnybrook Health Sciences Centre and lead author of the study.
Studies in which the sponsor drug was dosed higher were significantly more likely to show a positive outcome for that medication, as opposed to studies in which the sponsor drug was not dosed higher.
The team identified several possible explanations for the difference in dosages.
“One potential explanation is sponsorship bias, in which comparator drugs are dosed inadequately to increase the likelihood of greater benefit for sponsor drugs,” says Dr. Ayal Schaffer, Head, Mood Disorders Program at Sunnybrook.
"However, at the time sponsor drugs are initially tested, the 'typical dose' is not necessarily established which could also result in higher doses," he adds.
Another possible explanation is that newer antidepressants have fewer or more tolerable side effects than older ones, allowing for higher dosages.
It is an accepted research practice to use clinical trials to demonstrate that a new drug is as good as a low dose of a standard drug. However, one important issue that arises from these findings is how clinicians use individual studies to decide which medications to use for their patients. "By using a lower dose of the comparator drug in these trials, the results may lead to the false conclusion that a new drug is the same as or better than an optimally dosed comparator drug," says Dr. Sinyor.
The researchers suggest that journals should require mean final medication doses from authors as a prerequisite for publication. If a drug was dosed relatively higher than its comparator, articles should explicitly state that this has occurred, and should include a discussion of this issue in the main text.
"Studies should be more transparent about the issue of dosing, and the pharmaceutical industry, sponsors, journal editors, peer reviewers and clinicians need to pay greater attention to this issue," says Dr. Anthony Levitt, Psychiatrist-in-Chief at Sunnybrook.