I have a bad cough and clogged sinuses for over 3 months and am allergic to something in cigarette smoke. My doctor prescribed Allegra-D 24-hr, but Aetna decided it was an 'over the counter' drug, now I'm having a problem finding allegra-d 24-hour pills. So he prescribed clarinex d, 24-hour, but it doesn't work as well as allegra-d. why does fexofenadine and pseudoephedrine work better than loratadine and pseudoephedrine? and why is it so hard to find now?