What do you mean by "undoubtedly the most dangerous NMDA antagonist"
Are you saying DXM is dangerous?? i've done DXM like 20 times, havent had any problems at all...
Ketamine and DXM also act on NMDA receptors but are considered less dangerous than PCP.
DXM is by no means safe however, 20 times isn't much at all. If you were to do it several times a week you could eventually develop a temporary psychosis.