If i were to drink about half a glass of liquor is it safe to take nyquil and if not what can happen?

What's half a glass: There are 6 oz glasses and 18 oz. Glasses, and if you are talking about "straight" liquor, 4 oz. Of vodka in an 8 oz. Glass is almost 3 standard drinks. Nyquil is about 20% alcohol (or 40 proof), so 2 tablespoons or an ounce is essentially another 1/2 drink. It also contains dextromethorphan and an antihistamine, which may not react well with a lot of alcohol. There are alcohol-free cough syrups.