Two fatal cases of hyperpyrexia and coma (
symptoms similar to serotonin
syndrome) have occurred in patients taking phenelzine with
dextromethorphan (in overdosage in one case). Three other serious but non-fatal reactions occurred in patients taking
dextromethorphan with
isocarboxazid or phenelzine.
MAOIs are contraindicated with
dextromethorphan.