Consensus Guideline Based Therapeutic Drug Monitoring (TDM) in Psychiatry and Neurology

Therapeutic drug monitoring (TDM) is a valuable tool for tailoring the dosage of the prescribed medication(s) to the individual pharmacokinetic characteristics of a patient. In psychiatry and neurology, however, proven evidence that TDM should be used for treatment with the multiple neuropsychiatric medications is restricted to few compounds. Well-designed clinical trials on medical and economic benefits of TDM are rare. The use of TDM is limited in most countries to few antiepileptics, especially carbamazepine, phenobarbital and phenytoin, some mood stabilizers, especially lithium and valproic acid, some antidepressants, especially tricyclic antidepressants and some antipsychotics, primarily clozapine because these drugs have a narrow therapeutic index. On the other hand, specific indications and distinct problems can make TDM most useful for individualized pharmacotherapy with almost any neuropsychiatric drug. Potential benefits of TDM can, however, only be reaped if the method is adequately integrated into the clinical treatment process. The TDM expert group of the Arbeitsgemeinschaft für Neuropsychopharmakologie und Pharmakopsychiatrie (AGNP) issued consensus guidelines for the best practice of TDM in psychiatry and neurology. A first version was published in 2004. These guidelines were extended in 2011 and are actually updated (see: www.agnp.de). Exemplified by single cases it is shown here how to use TDM consensus guidelines for problem solving in psychiatry and neurology. Studies on depressed patients give evidence for tricyclic antidepressants, venlafaxine and citalopram that TDM could become a standard of care in psychiatry and neurology. There is potential to accelerate improvement. Reducing phases of suffering will not only have medical benefits for the patients but also an impact on costs for the health system which needs to be clarified by controlled studies.