How much Gauifensin does it take to get you sick?

Im not 18 so i cant buy the good dxm products so im stuck with whats in our house (regular medicine), the only problem with that is that it doesnt just contain dxm. i found this kind thats got Guaifenesin in it too so im wondering how much is going to make me sick. its those extended release capsule kind and its 1200 mg Gf for every pill. how many pills will it take to get me sick?