Traxoprodil (developmental code name CP-101606) is a drug developed by Pfizer which acts as an NMDA antagonist, selective for the NR2B subunit.

[5][6] Traxoprodil has been researched in humans as a potential treatment to lessen the damage to the brain after stroke,[7][8][9][10] but results from clinical trials showed only modest benefit.

[12] More recent animal studies have suggested traxoprodil may exhibit rapid-acting antidepressant effects similar to those of ketamine,[13] although there is some evidence for similar psychoactive side effects and abuse potential at higher doses,[14] which might limit clinical acceptance of traxoprodil for this application.

Traxoprodil showed ketamine-like rapidly-acting antidepressant effects in a small clinical trial of 30 patients with depression who were non-responders to 6 weeks of paroxetine treatment.

[15] The response rate was 60%, relative to 20% for placebo, and 33% of the participants met remission criteria by day five following a single administration.