Topamax is in a whole different class of drugs (antiepileptics). Doxepin is a tricyclic antidepressant, which will make you drowsy and most likely cause several unpleasant side-effects, dependent on dose and body weight. Trazodone (Desyrel) would have been a better choice
Edit: I read in the other thread you got just 10mg prescribed, so it probably won't do much or any bad/good at all, let's see.