Value and actuality of the prescription information for therapeutic drug monitoring of psychopharmaceuticals: a comparison with the medico-scientific evidence

Therapeutic drug monitoring (TDM) of psychopharmaceuticals, i.e., the assay of plasma concentrations, is a practical therapeutic application of pharmacokinetic principles in psychiatry. The prescription information (summary of product characteristics, SPC) is provided by pharmaceutical companies according to the requirements of regulatory authorities. The present study investigated the degree of agreement of German SPCs for 48 psychopharmaceuticals with the existing medico-scientific evidence in the area of TDM. For this aim, an empirical summary score of SPC content related to TDM (SPCC (TDM)) was calculated and compared with the level of recommendation of TDM (LOR) of the AGNP-TDM expert group consensus guidelines. Considerable disagreement was found between the information on TDM in SPCs and existing medico-scientific evidence, e.g., in the case of antidepressant and antipsychotic drugs. Even for well studied compounds, such as amitriptyline and clozapine, insufficient information on TDM is included in German SPCs. Small differences existed in the TDM-related information in SPCs of generic drugs with, however, much variance between Germany, Austria and Switzerland. Generally, it must be concluded that deficits exist in the preparation of German SPCs for psychopharmaceutical drugs with respect to empirical pharmacokinetic data, i.e., TDM-relevant information. It is recommended that SPCs of psychopharmaceuticals should be improved in terms of TDM-related information and that target plasma concentrations be adjusted according to the guidelines of the AGNP-TDM expert group. A higher level of good pharmacokinetic practice may be thus achieved