All I've got for the comedown is Vimpat (lacosamide). It makes me sleepy as hell when I'm sober, so hopefully it'll work to comedown from coke
I would advise everyone to not do this. It didn't work at a 1g dose which is the highest dose I had ever taken, so I took another 500 mg and that gave me double vision and insane dizziness. I didn't get any sleep til I took 100 mg of trazadone.