Crossover Design

A clinical trial design in which each participant receives all study treatments in a sequence, with washout periods between treatments, serving as their own control. Crossover designs reduce inter-individual variability, require fewer participants than parallel designs, and are particularly efficient for pharmacokinetic bioequivalence studies. They are inappropriate for diseases that change over time or treatments with long-lasting effects.

Examples

• Bioequivalence studies: 2-period, 2-sequence crossover comparing generic vs. branded formulations
• Analgesic efficacy: 4-period crossover comparing acetaminophen, ibuprofen, combination, and placebo
• Antihypertensive comparison: AB/BA crossover with 2-week washout between drugs