Study DesignGlossary Term
ICH E9
A clinical trial design in which participants receive multiple treatments in sequence, with each participant serving as their own control by receiving all study treatments during different periods.
The crossover design represents an elegant approach to clinical trial methodology in which the same participants receive each treatment under investigation during distinct study periods. By having participants serve as their own controls, this design eliminates between-subject variability, the differences among individuals that can obscure treatment effects in parallel-group studies. This within-subject comparison increases statistical power, often allowing smaller sample sizes to detect meaningful treatment differences.
In a typical two-period crossover, participants are randomized to receive either Treatment A followed by Treatment B, or Treatment B followed by Treatment A. A washout period separates the treatment periods to allow the effects of the first treatment to dissipate before beginning the second. The duration of the washout must be sufficient to eliminate any pharmacological carryover, typically requiring several half-lives of the study drugs. Analysis accounts for potential period effects and treatment-by-period interactions.
Crossover designs are particularly well-suited for studying chronic, stable conditions where the underlying disease state remains relatively constant throughout the trial. They are commonly employed in studies of symptomatic treatments for conditions such as hypertension, asthma, and chronic pain, where participants can return to their baseline state after treatment discontinuation. However, crossover designs are inappropriate when the treatment causes irreversible effects, when the disease naturally progresses or resolves over time, or when carryover effects cannot be adequately eliminated. The design also requires that participants complete all treatment periods for valid within-subject comparisons, making participant retention particularly important.
Antihypertensive study
"The blood pressure study employed a three-period crossover design in which each participant received the investigational drug, an active comparator, and placebo in randomized sequence, with two-week washout periods between treatments."
Bioequivalence study
"The bioequivalence trial used a two-way crossover design comparing a generic formulation to the reference product, with healthy volunteers receiving both treatments in random order separated by a one-week washout."
The fraction of an administered dose of a drug that reaches the systemic circulation unchanged, and the rate at which this occurs.
A group of participants in a clinical trial who receive a comparator treatment, placebo, or no treatment to serve as a baseline for evaluating the effects of the investigational intervention.
A systematic approach to increasing the dose of an investigational product during a clinical trial, typically employed in early-phase studies to identify safe and potentially effective dose levels.
A clinical trial in which both the participants and the investigators are unaware of the treatment assignments, providing maximal protection against bias in the conduct and assessment of the study.
The time required for the concentration or amount of a drug in the body to decrease by one-half, reflecting the combined effects of elimination processes.
ICH E9
A clinical trial design in which participants receive multiple treatments in sequence, with each participant serving as their own control by receiving all study treatments during different periods.
The crossover design represents an elegant approach to clinical trial methodology in which the same participants receive each treatment under investigation during distinct study periods. By having participants serve as their own controls, this design eliminates between-subject variability, the differences among individuals that can obscure treatment effects in parallel-group studies. This within-subject comparison increases statistical power, often allowing smaller sample sizes to detect meaningful treatment differences.
In a typical two-period crossover, participants are randomized to receive either Treatment A followed by Treatment B, or Treatment B followed by Treatment A. A washout period separates the treatment periods to allow the effects of the first treatment to dissipate before beginning the second. The duration of the washout must be sufficient to eliminate any pharmacological carryover, typically requiring several half-lives of the study drugs. Analysis accounts for potential period effects and treatment-by-period interactions.
Crossover designs are particularly well-suited for studying chronic, stable conditions where the underlying disease state remains relatively constant throughout the trial. They are commonly employed in studies of symptomatic treatments for conditions such as hypertension, asthma, and chronic pain, where participants can return to their baseline state after treatment discontinuation. However, crossover designs are inappropriate when the treatment causes irreversible effects, when the disease naturally progresses or resolves over time, or when carryover effects cannot be adequately eliminated. The design also requires that participants complete all treatment periods for valid within-subject comparisons, making participant retention particularly important.
Antihypertensive study
"The blood pressure study employed a three-period crossover design in which each participant received the investigational drug, an active comparator, and placebo in randomized sequence, with two-week washout periods between treatments."
Bioequivalence study
"The bioequivalence trial used a two-way crossover design comparing a generic formulation to the reference product, with healthy volunteers receiving both treatments in random order separated by a one-week washout."
The fraction of an administered dose of a drug that reaches the systemic circulation unchanged, and the rate at which this occurs.
A group of participants in a clinical trial who receive a comparator treatment, placebo, or no treatment to serve as a baseline for evaluating the effects of the investigational intervention.
A systematic approach to increasing the dose of an investigational product during a clinical trial, typically employed in early-phase studies to identify safe and potentially effective dose levels.
A clinical trial in which both the participants and the investigators are unaware of the treatment assignments, providing maximal protection against bias in the conduct and assessment of the study.
The time required for the concentration or amount of a drug in the body to decrease by one-half, reflecting the combined effects of elimination processes.