I'd like to balance this advice out with a snippet from Wikipedia (and it's NMDA, just FYI):Quote from: WikipediaNMDA receptor antagonists are a class of anesthetics that work to antagonize, or inhibit the action of, the N-methyl d-aspartate receptor (NMDAR). They are used as anesthesia for animals and, less commonly, for humans; the state of anesthesia they induce is referred to as dissociative anesthesia. There is evidence that NMDA receptor antagonists can cause a certain type of neurotoxicity or brain damage referred to as Olney's Lesions in rodents, although such damage has never been conclusively observed in primates like humans, however, in adolescent cynomolgus monkeys that were injected daily with the non-competitive NMDA antagonist, ketamine, there were some definite neurologic deficits observed.I'm not sure I'd take an NMDA antagonist long term. But that's just me.