Acetaminophen/dextromethorphan/doxylamine (Vicks Nyquil Cold and Flu) and melatonin are both over-the-counter medications that can make you sleepy. But they have some important differences. Nyquil Cold and Flu is a combination medication that treats symptoms of the common cold and flu, such as cough, sore throat, and fever, while melatonin is a dietary supplement used to help with sleep problems like insomnia and jet lag. Nyquil Cold and Flu contains three active ingredients: acetaminophen, dextromethorphan, and doxylamine, which work together to relieve pain, suppress cough, and reduce allergy symptoms. In contrast, melatonin is a synthetic version of a natural hormone that helps regulate sleep. Nyquil Cold and Flu is available in liquid and capsule forms, whereas melatonin comes in various forms, including pills, sprays, patches, and topical creams. Nyquil Cold and Flu can cause side effects like sleepiness and dizziness and should not be taken with other medications containing acetaminophen (Tylenol). Melatonin is generally well-tolerated but can cause daytime drowsiness and headaches. Additionally, melatonin can interact with medications like oral contraceptives, so it's important to check with your provider or pharmacist before starting it.