http://www.medications.com/effect/view/31722 Rx for 10mg Flexeril 6/19/08 for severe muscle spasms upper back and neck. Took one tablet 6/19 2pm, one tablet 6/19 10pm. Slept well, but woke up with spasms worse than ever. Took 2 10mg tablets 6/20 7am and slept ALL day - 16 hours in a 24 hour period. T