Here is an article discussing the seizure potential of tramadol and its metabolites.
http://jpet.aspetjournals.org/cgi/reprint/325/2/500.pdf
The fact that one of the enantiomers of tramadol might be particularly
potent (potency in terms of seizure potential) was not found to be the case; the (+)- and
(–)enantiomers were about equipotent to tramadol. The
fact that the M1 (aka o-desmethyltramadol) metabolite or its enantiomers might be particularly potent was also not found to be the case. M1 and
its (+)- and (–)enantiomers were less potent than tramadol
http://jpet.aspetjournals.org/cgi/reprint/325/2/500.pdf