Dahan A et al. – Pharmacological treatment of chronic (neuropathic) pain is often disappointing. In order to enhance the insight in the complex interaction between analgesic drug and chronic pain relief, the authors performed a pharmacokinetic–pharmacodynamic (PK–PD) modeling study on the effect of S(+)–ketamine on pain scores in Complex Regional Pain Syndrome type 1 (CRPS–1) patients...Long–term S(+)–ketamine treatment is effective in causing pain relief in CRPS–1 patients with analgesia outlasting the treatment period by 50 days. These data suggest that ketamine initiated a cascade of events, including desensitization of excitatory receptor systems in the central nervous system, which persisted but slowly abated when ketamine molecules were no longer present. [more...]