Wash-Out Period: Your Questions, Answered
October is health literacy month, and to celebrate, we’ve been defining common terms used in clinical trials as part of our “word of the day” series on Twitter. Last week, we posted a Twitter poll, asking for your input on which words to define.
More than 600 of you voted, and the clear winner was “wash-out period.” The basic definition is pretty straightforward: A pre-defined period of time before or during a clinical trial when participants receive no active medication is called a “wash-out period.”
But it was the reaction of one respondent that really made us pause:
Based on that response, we offer a deeper discussion of WHY clinical trials often include a wash-out period. The short answer is that a wash out period helps affirm that effects seen in a clinical trial are attributable to the investigational drug, not previous medication.
A little more context
The purpose of a clinical trial is to measure the effects of an investigational drug in people and answer questions like: How is it metabolized? Does it have a measurable effect on the disease it’s designed to treat? Is that measurable effect better than the already available treatments? Are the side effects manageable?
As with any scientific investigation, we try to minimize the number of variables as much as possible so that we can be sure we are attributing the effects of our intervention to the right cause. In the case of clinical trials, we want to be sure the effects we measure are caused by the investigational drug, not the latent effects of some medication taken before the start of the trial. We also want to protect people from potential drug interactions (known or unknown). And so we often make it a requirement in the entry criteria that a certain amount of time must pass since the last dose of a prior medication was taken.
Here is a specific example: In an ongoing Phase 3 study sponsored by Lilly, people with plaque psoriasis who volunteered to participate were required to stop phototherapy and/or any previous systemic therapy at least 4 weeks before enrolling in the trial.
The down side
These kinds of long wash-out periods can also be a deterrent to study participants, especially those who have been in multiple trials. For example, people with cancer don’t want to wait for long periods between treatment regimens, for fear their cancer will grow.
The length and requirement for wash-out periods illustrates one of many ways that we have to balance the desire to make clinical trials a pure science with the needs of the patients who volunteer to participate in those trials.
If you’d like to read even more about considerations for wash-out, check out this resource from the University of Iowa Institutional Review Board manual.
Check out our Twitter feed for the definitions of the other two words in our poll (double-blind study and healthy volunteers).
Blog post originally appeared on LillyPad.