Dioxadrol is the antidepressant agent. It was synthesized in 1966 and pharmacologically evaluated as a local anesthetic and general anesthetic drug. It was shown that dexoxadrol binds with high affinity toward NMDA receptor. Dioxadrol exists in four isomeric forms. alpha-(+)-Dioxadrol (dexoxadrol) showed phencyclidine (PCP)-like activity in rhesus monkeys trained to discriminate subcutaneous administration of ketamine, but neither alpha-(-)-dioxadrol (levoxadrol) nor beta-(+/-)-dioxadrol showed such activity. During clinical evaluation, it became obvious that non-tolerable side effects (retrograde amnesia, psychotomimetic effects) are associated with the application of dexoxadrol. These observations have led to termination of clinical development.