Is valium an 'antidote' for cocaine?

Fuck No!

No, but benzos are often taken after a heavy night on the powder, to knock you out so you don't have to deal with the comedown/crash.

They've been know to be used for ODs on stims, but any CNS depressant will work in basically the same way. (i.e. h, oxy, etc.)

No, but It and some bud will help your ass get to sleep.

good for coemdowns

Sometimes, when I take a heroic dose of psychedelics, it makes me feel more comfortable just having a few Valiums in my pocket.

Well valium is an anticonvulsant isnt it? Wouldnt it help with the seizures if one was oding?

I don't believe so, but I do think Klonopin is. It also happens to be a Benzo, so it's closely related to Valium. All Benzos are commonly used during comedowns to help prevent that edgy feeling, anxiety, rage, and uncomfortable insomnia. I personally don't recommend it, as it's not good for your body (Especially your heart) to mix stimulants and depressants. That and Valium has like an 80 - 100 hour half life...