My son was prescribed clonidine .5mg.2day he was taken off clonidine & put on guanfacine 1mg. can he take guanfacine 2nite after taking clonidine a.m.?

Probably: I suspect your son was on 0.05 mg of Clonidine 2x a day; that's about the same as 1 mg of guanfacine. They're in the same family of medications, working on the same system. Talk with his doctor, but switching over that dose should not cause a problem, especially since Guanfacine typically has fewer side effects. The biggest concern is a potential spike in BP from stopping Clonidine too fast.