IME: Yes. I used to do it all the time. And opiates. And alcohol. And some times meth too. Some times acid and/or mdma. 60mg of valium will calm any edginess. I also used to take xanax and clonazepam at the same time.
It's true, you should let the vallies do their thing for their 4-5 hour duration or they will simply overwhelm the coke
it's a safe combo, just not a very smart one