Has this happened to anyone? I have been taking Ambien for more than 6 years and always got a great nights sleep. (6.25 mgs.) Always worked fine. Last month I picked up my refill as usual. Took one, no sleep. Next night, same thing. Same thing for a week. Unfortunately, I had to go into the hospital for a bad UTI. I asked for Ambien and they gave me a 5 mg. I slept like a baby. Even with interruptions for vitals, went right back to sleep. Came home, took the 6.25 mg. No sleep. My dr. says it's impossible. "All mags. have to sell the same ingredients." I asked my dr. to prescribe the 5 mg. He did. I slept. Any opinions??