Can i take 2 10 mg flexeril (cyclobenzaprine hcl) at one time? is there a big risk with doing that?

Don't take 20mg: The maximum dose of flexeril is 10mg 3 times per day. A higher dose will give a higher peak level in your blood, and could cause sedation, cardiac arrythmias, and other serious stuff. Flexeril is a weak muscle relaxant. In my experience, people with severe spasm often do better with baclofen, or robaxin, (methocarbamol) or tizanidine.