Acetaminophen is used to decrease pain. Dextromethorphan is used to stop the cough.
Pseudoephedrine is used to dry up nasal stuffiness.
Acetaminophen decreases the production of chemicals called prostaglandins. This decreases pain. Dextromethorphan suppresses the cough center in the brain. Pseudoephedrine shrinks swollen nasal tissue and opens up passages. Sinus drainage is increased by this.