I have had my dogs on Tramadol -- and sedation has always been a side effect from that drug.  In some cases, some dogs may experience an opposite effect -- but that is a rare exception.  No musher sees Tramadol as an effective pain relief medication for competition -- if pain medications were allowed by race rules, there are more effective pain medications than that.  And dogs don't become constipated from Tramadol.  Human beings become constipated after being on strong opiate medications - but dogs do not react in the same way. And, btw - Dallas is a very knowledgeable musher and honest -- and even if he weren't, he would not risk drugging his dogs hours before a scheduled drug screen.