This research was being done in an effort to find alternatives to dopamine agonists,
4) in addition to dipyradimole, the article also mentions methotrexate as an adenosine antagonist. It would be interesting to find out how many rheumatoid arthritis patients on this drug also have RLS, and
5) finding an effective ENT1 antagonist is very complicated since adenosine receptors exist in so many critical systems in our bodies.
The researchers that structured the dipyridamole trial we're obviously aware that there were other ENT 1 antagonists that could be used. I imagine that they picked dipyridamole because its side effect profile was probably better than most of the other already released ENT 1 antagonists.
The comment about methotrexate is an example. Methotrexate has been used for many years as a treatment for autoimmune diseases and certain forms of cancer. However it has very serious potential side effects including pulmonary fibrosis and immune system compromise. For the general physician treating RLS patients, use of methotrexate would have to be fantastically better than dipyridamole for the treatment of a non-lethal condition like RLS. (Though I'm sure some of us would dispute the "non-lethal" nature, particularly those of us that have to drive or contemplated suicide after having a bad night.)