How much NyQuil night time cough medicine is an overdose?

Yeah there is no law telling you that you can't so techinically you can. But if you want to know the correct response you should ask a doctor not the lunies on wikianswers.

I'm not to familiar with nyquil, but like all medication it will say the dosage instructions somewhere on the box.

it depends on what u take.

There is no guarantee that a cough syrup will get you high in the first place, depending on its ingredients. And WikiAnswers does not give answers on how to get high.

Nothing, you may feel a bit bloated. OTC medicine like cough medicine are so light nothing will really happen. If you do see signs, call poison control center.