DOSING OF ANTIDEPRESSANTS - THE UNKNOWN ART

Data from a therapeutic drug monitoring service, in total 2,393 observ ations in 1,606 patients, were used to analyze factors associated with the prescribed daily doses of the tricyclic antidepressants amitripty line and nortriptyline. The achieved concentrations in plasma were eva luated in relation to suggested therapeutic ranges. The doses of both drugs were greatly reduced with increasing age, despite the fact that age is of minor importance for their kinetics. Interactions with conco mitantly given drugs were not handled by dose adjustments of the antid epressant. Therapeutic drug monitoring increased the proportion of con centrations within the therapeutic range for patients on amitriptyline , but not for those on nortriptyline. The large interindividual kineti c variability for most antidepressants requires individualized dosing, but this individualization is performed on incorrect grounds.