That started happening to me a few years ago; went to a neurologist and it
turned out it was caused by a bone spur in my neck. Had surgery last year to
have the spur removed and now it's gone. Still have the original rigid
spasticity from my CP, but even that seems to have eased up a bit.
I realise this is not what you're asking. But I do take 1 tablet of Zannaflex
for the spasticity at bedtime, as it makes me sleepy, too.
Kyle's right in that Vioxx is an anti-inflamatory and not an anti-spasmodic
drug, so perhaps you should talk to your doctor.