What is Telfast Decongestant (Allegra D) used for?  
 
Telfast Decongestant (ALLEGRA-D) should be administered when both the antihistaminic properties of fexofenadine hydrochloride and the nasal decongestant properties of pseudoephedrine hydrochloride are desired

Allegra works on your seasonal allergy symptoms: your itchy, watery eyes, plus sneezing and runny nose. But if you find your nose is stuffed up too, you should consider Allegra-D. Allegra-D has the same antihistamine as Allegra with the added relief of a decongestant.

Because Allegra-D contains pseudoephedrine (the decongestant in most over-the-counter allergy medicines), Allegra-D must not be taken if you are also taking MAO inhibitors (medicines that treat depression) or if you retain urine or have glaucoma, severe high blood pressure, or severe heart disease.

Also, let your doctor know before you take Allegra-D if you have high blood pressure, diabetes, heart disease, glaucoma, thyroid disease, impaired kidney function, or symptoms of an enlarged prostate such as difficulty urinating. The most commonly reported adverse experiences with Allegra-D compared to pseudoephedrine alone were headache (13.0% vs 17.4%), insomnia (12.6% vs 13.3%), and nausea (7.4% vs 5.0%).