Hi. I have taken Xyzal for several years to control my chronic cough. it s the only thing that seems to work. However, in the last 18 months, my kidney GFR has fallen to 58, and stayed there. I have no other risk factors for chronic kidney disease---no diabetes, my blood pressure has always been normal, my cholesterol is within the normal range and I have no heart conditions. Could this low GFR be caused by Xyzal?