Key takeaways
Mucinex DM (guaifenesin / dextromethorphan) and Nyquil Cold and Flu (acetaminophen / dextromethorphan / doxylamine) are both over-the-counter medications that help relieve coughs. They both contain dextromethorphan, which is a cough suppressant. However, they belong to different medication classes and treat different symptoms. Mucinex DM is an expectorant and antitussive combination used to relieve coughs and loosen mucus from minor throat or lung irritation, like the common cold. It comes in tablets, dissolvable granules, and liquid forms. Nyquil Cold and Flu combines an analgesic, a cough suppressant, and an antihistamine to relieve cold and flu symptoms, such as sore throat, fever, and runny nose. It is available in liquid and capsule forms. Mucinex DM is typically taken every 4 to 12 hours, depending on the formulation, while Nyquil is taken every 6 hours. Mucinex DM can cause side effects like dizziness and drowsiness, while Nyquil may cause sleepiness and dizziness due to the antihistamine doxylamine. Both medications should not be taken with monoamine oxidase inhibitors (MAOIs) due to the risk of serotonin syndrome.
