List of NDC products with proprietary name clarinex-d 12 hour. This medication is used to relieve allergy symptoms such as watery eyes, runny/stuffy nose, itching eyes/nose, and sneezing. It contains 2 medications: desloratadine and pseudoephedrine. Desloratadine is an antihistamine and works by blocking a certain natural substance (histamine) that your body makes during an allergic reaction. Pseudoephedrine is a decongestant and works by narrowing the blood vessels in the nose to decrease swelling and congestion. This medication is not recommended for use in children younger than 12 years of age due to the large amount of pseudoephedrine in it.