Hi Rae,

I've answered this in two of the other places you posted it. It partly depends on whether the muscle involved is smooth or skeletal; antispasmodics work better for the former, while muscle relaxants (like Flexeril/cyclobenzaprine work better for the latter.

http://en.wikipedia.org/wiki/Antispasmodic
http://en.wikipedia.org/wiki/Muscle_relaxer

Baclofen is used for spasticity, which is also generally a skeletal issue but slightly different than spasm.

http://en.wikipedia.org/wiki/Spasm
http://en.wikipedia.org/wiki/Spasticity

In some situations, like when a myofascial triggerpoint is involved, we've found that myofascial triggerpoint therapy (they call it "massage" but it can hurt like cuss) can work better, and last longer, than meds - other times not.

http://en.wikipedia.org/wiki/Myofascial_release

Doc