Even over-the-counter medications like cough syrup can have harmful interactions that vary with each person when combined with alcohol according to WebMD. Side effects can include everything from drowsiness, dizziness, fainting, headaches, nausea, vomiting and fluctuations in blood pressure to liver damage, internal bleeding, heart problems and depression.
Because hundreds of commonly used medications, including cough syrup, can interact negatively when mixed with alcohol, it is important to read the instructions and warnings on the labels of all medication, whether over-the-counter or prescribed by a physician. It is also important to speak to your healthcare provider or pharmacist if you have any concerns or questions. If you experience side effects while taking any medicine, cease using it immediately and seek professional advice.