Advantages of Parallel Design Over Crossover Design in the Study on Effects of Cannabis on Driving in Healthy Adults

• Activity Number: 251 - SPEED: Biopharmaceutical Methods and Application I, Part 2
• Type: Contributed
• Date/Time: Monday, July 29, 2019 : 2:00 PM to 2:45 PM
• Sponsor: Biopharmaceutical Section
• Author(s): Anya Umlauf* and Barth Wilsey and Thomas Marcotte and Florin Vaida
• Companies: UC San Diego and UC San Diego and UC San Diego and UC San Diego
• Keywords: power; study design; crossover; parallel-arms; cannabis research

Abstract

Legalization of cannabis for recreational use in many states created a need to study cannabis effects on driving performance. A double-blind parallel-arms (PA) study was designed to compare driving performance of healthy adults after being administered one of three treatments: 0% (placebo), 5.9%, or 13.4% ?9-tetrahydrocannabinol (THC) smoked cannabis. The participants’ performance on a driving simulator is being measured prior to THC administration (baseline) and at four later time points. Power was estimated under PA design and a crossover design for testing a hypothesis that changes in driving from baseline to post-smoking (outcome) differ between doses. Subjects serve as their own control in both designs as each visit consists of a baseline measurement and follow-up measurements. A PA study with n participants per arm (total=3n) has the same power as a crossover study involving 3 visits with n participants. Thus, compared to the PA design, the crossover design has no clear advantages, and important practical disadvantages, including learning effects, participant drop-out, increased study duration for inclusion of wash-out periods.