The drug Zolpidem. Has a sedative (sleep-inducing) effect when taken. Used by Air Force operators to help them calm down after taking stimulants to stay awake during long missions. The opposite of a [go-pill].
Also used before a mission to calm nerves and promote sleep.
> After flying for 120 hours nonstop, having taken many [go-pill]s in the process, the pilots required a no-go pill to help them sleep.