Ketamine--can chronic use impair memory?

Ketamine, a congener of phencyclidine (PCP), can produce a range of psychological effects which have led to its nonmedical use. Recent discoveries concerning the effects of ketamine and similar substances in the brain suggest that they may interfere with memory processes when given acutely and may affect synaptic plasticity when given chronically in high doses in certain animal models. It is thus of interest to examine the consequences, if any, of chronic use in humans. A case is here presented of long-term, high-dose ketamine use, in which the user described impaired recall and attention, and a subtle visual anomaly persisting after cessation of the habit. This history is considered in the context of other relevant studies.