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. Chlorpheniramine and hydrocodone is a combination medicine used to treat runny nose, sneezing, watery eyes, and cough caused by allergies or the common cold. Chlorpheniramine and hydrocodone may also be used for purposes not listed in this medication guide.