If I could add one point, it's equally illegal now to be behind the wheel driving impaired by alcohol, as it is to be behind the wheel impaired by a prescription drug you're taking for medically necessary purposes completely legally and lawfully. We know many over-the-counter drugs say that they could impair you. Lawful or illegal, if the substance causes impairment, you shouldn't be driving.
On June 13th, 2017. See this statement in context.