Excessive Sleep, Vomiting, Fever After Taking Histatussin. Side Effect?

my son and i went out yesterday he was fine before we left he ate his breakfast and took his medicine after.after reaching home he had a patty and soda , soon after he finish he took his medicine which is quater teaspoon of histatussin,half and hour later he went to bed. about 3-4hours later he woke up he came and laid in my lap,i ask him if he want somthing to eat he said no he would just like a drink of water,after he went to the bathroom to urinate when i got up to check on him he had vomited.i felt him and he was hot,even now he s hot.do you think tis a side effect from the medicine.