Washout Period

The time interval between treatment periods in a clinical trial during which no study drug is administered, allowing the pharmacological effects and residual drug concentrations from the prior treatment to dissipate before the next treatment begins. The washout period is typically set at 5-7 elimination half-lives to ensure negligible carryover. Adequate washout is critical in crossover study designs to prevent confounding.

Örnekler

• Crossover NSAID study: 2-week washout between ibuprofen and naproxen periods
• Antidepressant switching: 5-week washout after fluoxetine (long half-life metabolite) before starting MAOI
• Amiodarone: requires months of washout due to extremely long half-life (40-55 days)