Shortness of breath is one of the listed side effects of Baclofen Kitty, but I'm not so sure about the joint pain. I know muscle pain is a rare possibility, but I've not heard of it spreading to joints. That doesn't mean it can't of course, but it really concerns me that you had breathing problems. I'd not take any more of the tablets until you check with your doctor, because the next reaction could be far worse.

I hope that helps a bit, and if you want more information, why don't you ask mrsD over in the Medication forum?