Medical cannabis and driving.

BACKGROUND: Medical cannabis use is increasingly common in Australia. Patients and physicians need to be aware of the important implications that such use may have for driving. OBJECTIVE: The aim of this article is to briefly review the scientific evidence regarding cannabis and driving impairment and discuss current legal issues affecting patients, as well as to update physicians on relevant issues and the best guidance to offer their patients. DISCUSSION: Delta-9-tetrahydrocannabinol (THC) impairs driving performance and can increase crash risk. These effects are more pronounced in people who use THC occasionally and can last for up to eight hours with oral THC products. There is no evidence that cannabidiol (CBD) impairs driving. Patients using THC-containing products should avoid driving and other safety-sensitive tasks (eg operating machinery), particularly during initiation of treatment and in the hours immediately following each dose. Patients may test positive for THC even if they do not feel impaired, and medical cannabis use does not currently exempt patients from mobile (roadside) drug testing and associated legal sanctions.