Key takeaways
Acetaminophen/dextromethorphan/phenylephrine (Dayquil) and acetaminophen/dextromethorphan/doxylamine (Nyquil) are both over-the-counter medications used to relieve symptoms of the common cold and flu, such as cough, sore throat, headache, minor aches, and fever. However, they have some important differences. Dayquil contains phenylephrine, a decongestant that helps relieve a stuffy nose, while Nyquil contains doxylamine, an antihistamine that can make you sleepy. This makes Dayquil better for daytime use and Nyquil better for nighttime relief. Dayquil is typically taken every 4 hours, while Nyquil is taken every 6 hours. Both medications are available in liquid and pill forms, but they have different dosing instructions. Common side effects of Dayquil include stomach upset and nervousness, while Nyquil can cause sleepiness and dizziness. You should avoid alcohol or other products containing acetaminophen while you are taking either medication.
