Clinical Design in Chronic Pain Studies

The authors of this study suggest that enriched enrolment with randomised withdrawal (EERW), be used in drug studies, particularly analgesics for chronic pain patients. Individual response to a drug can be influenced by genetic differences, particularly in the metabolism of drugs. The authors feel that conventional clinical trials may not be adequate in assessing efficacy of a certain drug given some subjects may be non-responders to the drug. The risk is that false conclusions may be made due to lack of efficacy in traditional studies. Consequently, some drugs may not be approved that could be of benefit to those that are responders.

EERW designs are more sensitive than conventional designs that lower the proportion of responders. In typical randomised trials, the risk is that non-responders dilute the outcomes in terms of efficacy of a drug. The authors suggest that patients should be trialed on a drug first and those that have satisfactory response and at worst tolerable adverse effects are then randomised into the study. After randomisation, they are compared to a control group.

The authors feel that the EERW study design, using only those subjects that are known to be responders is more ideal. This may ensure that people will not be denied an effective treatment simply because results are diluted by non-responders in more traditional study designs.



References: H.J. McQuay et al. Enriched enrolment with randomised withdrawal (EERW): Time for a new look at clinical trial design in chronic pain. Pain 2008. Volume 135. Pp. 217-220.