Nyquil

**Semantic type:** Pharmacologic Substance

**Definition:** A commercial combination preparation, by Vicks, containing acetaminophen, dextromethorphan hydrobromide and doxylamine succinate used to relieve symptoms of cold and flu. Acetaminophen exerts analgesic and antipyretic actions by inhibiting prostaglandin synthesis. Dextromethorphan exerts antitussive activity by raising the threshold for coughing in the cough center. Doxylamine succinate, an antihistamine, blocks the effects of histamine, thereby treating symptoms such as sneezing, itchy, watery eyes, runny nose, itchy throat and causes drowsiness.