"i&#039;ve been on ambien cr (zolpidem xr) for years. it always worked. until it didn&#039;t. i have insomnia because of fibromyalgia and a bad back which wakes me every time i turn over. but it loses its efficacy after 6-7 months. doctor switched me to lunesta and it did nothing. it was as if i took a placebo. went back to the zolpidem xr but i&#039;m now back to having built up a tolerance again. doc put me on temazepam but it&#039;s like nothing too. it stinks not being able to sleep or stay asleep."