Dextromethorphan Hydrobromide, Cetirizine, Phenylephrine, Ambroxol, Guaifenesin, and Sodium citrate. Dextromethorphan hydrobromide is a cough suppressant that acts on the cough center in the brain. It helps to reduce the urge to cough by inhibiting the brain signals that trigger the cough reflex. Cetirizine blocks the effects of histamine, a chemical the body produces in response to allergens. It helps to reduce allergy symptoms, such as sneezing, runny nose, and itchy or watery eyes. Phenylephrine is a decongestant that constricts blood vessels in the nasal passages, reducing swelling and congestion. Ambroxol, guaifenesin, and sodium citrate work by thinning and loosening the mucus in the airways and clearing congestion.