Chlorpheniramine is an antihistamine that reduces the natural chemical histamine in the body. Histamine can produce symptoms of sneezing, itching, watery eyes, and runny nose. Hydrocodone is a narcotic cough medicine. Phenylephrine is a decongestant that shrinks blood vessels in the nasal passages. Dilated blood vessels can cause nasal congestion (stuffy nose). Chlorpheniramine, hydrocodone, and phenylephrine is a combination medicine used to treat runny or stuffy nose, sinus congestion, and cough caused by the common cold or flu. Chlorpheniramine, hydrocodone, and phenylephrine may also be used for purposes not listed in this medication guide.