Nitrofurantoin
"Took first pill and symptoms went away. Second pill I started getting tingling and burning in my back 4 hours after taking the medication. Second pill made the back symptoms go away but introduced a intense pressure in my bladder and pelvic area. 4 hours later it went away then the back pains started again, and 10x worse. My spine had sharp spike of pains in it. I was rushed to ER and was told to stay off the pills. They didn't know what caused the reaction (obviously they can't admit it was the pill) and sent me home with some ativan to relax my body. Stopped for 2 days and the spiking pains are still in my back and spine on and off. Also felt weak and lost feelings in my legs.

Be careful, if you see symptoms stop right away. Do not risk!"