Clonidine
"I have tried numerous drugs for RLS, including Neurontin, Klonopin, Lyrica, Mirapex, and clonidine (and possibly 1 or 2 others).  Clonidine started out positively, giving me more relief than Neurontin.  However, unfortunately I developed a very rare severe side effect called Stevens-Johnson Syndrome (a.k.a. toxic epidermal necrolysis), which has a high death rate.  Needless to say, clonidine was D/C'd, and after lengthy treatment for SJS, I (cautiously!) tried a different drug.  Ultimately, Mirapex and Lyrica have been the best, with approx. equal effectiveness."