Most meds, like baclofen, can reach a point of ineffectiveness because the nature of MS is attacks on the CNS. Nerve caused problems can be difficult to treat, especially long term.
Whenever there is a change, as you noted, I would always let the doctor know because they may want to change the med or stop the med or change the dosage.
You might try doing some leg stretching and make sure that you are not too warm. Though you work at a desk, you might need a fan blowing across your legs. I sleep best with my legs uncovered and most of my summer is spent in shorts. Stretching and low impact exercises are somethings you can do which help many MSers.
Leg throbbing 
