than 5 decades [ 521 , 522 ] , growing evidence suggests that improving the way the available medications are administered may bring substantial benefi t to patients [ 45 ] . Evidence-based guidelines for optimum treatment have been published during the last decade [ 23 , 46 , 101 , 204 , 205 , 221 , 234 , 254 , 276 , 284 , 582 , 585 ,748]. A valuable tool for tailoring the dosage of the prescribed medication(s) to the individual characteristics of a patient is therapeutic drug monitoring (TDM). The major reason to use TDM for the guidance of psychopharmacotherapy is the Introduction ▼ In psychiatry, around 130 drugs are now available which have been detected and developed during the last 60 years [ 54 ] . These drugs are eff ective and essential for the treatment of many psychiatric disorders and symptoms. Despite enormous medical and economic benefi ts, however, therapeutic outcomes are still far from satis factory for many patients [ 5 , 6 , 396 , 661 ] . Therefore, after having focused clinical research on the development of new drugs during more Therefore the TDM consensus guidelines were updated and extended to 128 neuropsychiatric drugs. 4 levels of recommendation for using TDM were defi ned ranging from "strongly recommended" to "potentially useful". Evidence-based "therapeutic reference ranges" and "dose related reference ranges" were elaborated after an extensive literature search and a structured internal review process. A "laboratory alert level" was introduced, i. e., a plasma level at or above which the laboratory should immediately inform the treating physician. Supportive information such as cytochrome P450 substrateand inhibitor properties of medications, normal ranges of ratios of concentrations of drug metabolite to parent drug and recommendations for the interpretative services are given. Recommendations when to combine TDM with pharmacogenetic tests are also provided. Following the guidelines will help to improve the outcomes of psychopharmacotherapy of many patients especially in case of pharmacokinetic problems. Thereby, one should never forget that TDM is an interdisciplinary task that sometimes requires the respectful discussion of apparently discrepant data so that, ultimately, the patient can profi t from such a joint eff ort. This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited. considerable interindividual variability in the pharmacokinetic properties of the patient [ 524 , 526 ] . At the very same dose, a more than 20-fold interindividual variation in the medication's steady state concentration in the body may result, as patients diff er in their ability to absorb, distribute, metabolize and excrete drugs due to concurrent disease, age, concomitant medication or genetic peculiarities [ 61 , 94 , 310 , 311 , 334 , 335 , 374 ] . Diff erent formulations of the same medication may also infl uence the degree and temporal pattern of absorption and, hence, medication concentrations in the body. TDM uses the quantification of drug concent...
