Is there a therapeutic window with some antidepressants for analgesic response?

Most antidepressants and anticonvulsants used in chronic pain syndromes have dose- and concentration-response curves developed for their application to treat psychiatric disorders. Because these are important clinical tools in medication management of psychiatric syndromes, it is reasonable to expect that utilizing concentration-effect relationships and known sources of pharmacokinetic variability for determining doses for analgesia may also improve treatment tolerability and outcomes. Efforts to identify dosing "therapeutic windows" or minimum "thresholds" for analgesic efficacy have provided useful guidance for initiating treatment, reducing toxicity, and assisting with decision making in the face of limited therapeutic response. This article reviews the strengths, limitations, and potential of therapeutic drug monitoring of antidepressants and anticonvulsants as analgesics for selected chronic pain syndromes.