Elaborate?
Mixing phenethylamines with DXM is notorious for having unsafe and/or unpleasant side effects. Phenthylamines, like 2c-e share some pharmacological similarities with amphetamines, and are capable of producing cardiovascular anomalies and dangers, as well as running a general risk for serotonin syndrome when combined with DXM. Of course phenethylamines differ from each other in a variety of ways, and the risk profile for each will vary similarly. Despite that, the potential for danger is quite considerable when mixed with DXM, especially when the heart is concerned. Discretion should always be used when taking research compounds, which generally have little to no human or animal testing whatsoever, ESPECIALLY in combination with something like DXM, which itself has such a varied and often unpredictable pharmacological profile (particularly in combination with other drugs)
Edit: This is more so to do with DXM and 2c-e, not dissociatives in general.