Fexofenadine
"I started Allegra-D 12 hour in 1999 for allergies that left me with migraines & a neck so stiff that I could barley turn my head. Allegra-D 12 hour was a miracle & one tablet a day brought me back to fully functional.

It worked great for 15 years. But in summer of 2015, something changed. I would get a box that didn't work as well, then a box that worked just fine.  I emailed the manufacturer to ask if they had changed binders / fillers that might make it harder to metabolize the active ingredients. Of course they said "no". 

 Since summer of 2015, Allegra-D has been about as effective as taking a sugar pill. Don't waste your money. Email the company, demand they go back to the old formulation."