I find that B12 is the culprit when my legs shake. It has to do with the vitamins effect on nerve endings.
There's a lot out there explaining this. Maybe the drugs are depleting the B12. I find that most doctors do not know these basics yet they feel competent to prescribe the drugs.
B12 is a water soluble vitamin so you can take 1,000 mcg and see if it helps. May take a few days to show a change if you are very depleted. Any excess would just wash out of you.