Clinical Research Glossary

wash-out wash-out


A time before starting a study treatment when a person stops taking other medicines.

Example of wash-out in a sentence

A wash-out period removes certain current medications in the body so that they don’t interfere with the study treatment.

More Info

In research, a wash-out is a time when medication is stopped so it can be cleared from a person’s body before the study intervention is given.

A wash-out period makes sure that the medication and the study intervention don’t interact and increases the study’s safety. it also helps to show that effects observed in a study are from the study medication and not previous, unrelated medications.

Not every study has a wash-out period. When a study has a wash-out period it is a pre-set time that depends on the protocol and what medicines the person is taking.

Other info to think about when joining a study

Whether a research study requires a wash-out will be described in the consent form and the study team will discuss this with you.

It will be important for you to ask if you will have to go through a wash-out period and how that might affect you if you have been taking medications regularly before starting the trial. It could be important to discuss this with your regular doctor to let them know you will be stopping your routine medications.

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