However the entire bottle of NyQuil only has ~5 grams of acetaminophen in it and toxicity is around 200mg/kg. So unless he drinks another bottle tomorrow or weighs 55 pounds, he'll probably survive.
200mg/kg is a pretty high estimate even for an adult and that would be a marker of acute toxicity. I would have gone with 150mg/kg, but regardless, liver
damage can occur at doses much lower than that. Not saying that you're wrong -- he would survive an overdose of just 5000mg of paracetamol, but exceeding 3000mg in a single
day can be dangerous for a
fully grown adult.
More drug science:
That is an 8 fl oz bottle (240ml) which has 8 standard doses of cough syrup in it. In each dose, as it says on the back, there is a disproportionately high dosage of acetaminophen (higher than the 'maximum strength' pills available on the market, which are maxed at 500mg rather than 650), 30mg of 'the good stuff', and 12.5mg of an antihistamine.
So, since we've covered that he won't die from acetaminophen based liver toxicity, let's check out the antihistamine. Doxylamine is a first generation antihistamine which means it's one of those fun ones that knocks your ass straight out. You know, since it's nyquil, not dayquil. Two doses of this (25mg) is the recommended dose for insomnia over the age of 13. Under 13, this is too high of a dose. He's pretty close to 13 though, so I'd guess that if 2 doses can hurt a 13 year old, 8 doses may harm a 16 year old. But, more than likely, it'll just knock his ass out and he won't get to 'enjoy' his DXM.
Now there's the Dextromethorphan HBR. 30mg times 8 doses is a good 240mg. According to
erowid this sits comfortably at the start of a 'common' dose. Almost without fail this will cause vomiting and dizziness. On the up side, if he can get over the sensation of spinning and puking, he might feel some happiness. Congratulations to him.
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