What Could Happen From Drinking Too Much Cough Syrup?

WebMD explains that the biggest risk from drinking too much cough syrup is overdose on DXM, a common ingredient in nearly all over-the-counter cough medicines. DXM overdose may result in impaired vision, sweating, fever, disturbed breathing, irregular heart beat, blood pressure irregularities, stomach upset, impaired mental function and hallucination among other serious side effects.