I have RLS (and Periodic Involuntary Limb Movement). I have found it is usually controlled by a dose of 2000 IU of Vit D3. I started at 4000 IUs and reduced until I found the 2000 IUs worked fine most of the time (and when it doesn't I take 100mg of Gabapentin). It might be worth trying instead of a prescription med. Might work, might not but no harm in trying. I wish your husband good luck. This is a miserable syndrome.