3.1 Study population
A total of 132 antidepressant users were identified from the B-PROOF cohort. Of those, 59.8% reported a fall during follow up. InTable 1, the baseline characteristics of fallers and non-fallers in antidepressant users are shown. Fallers were more often female, experienced more falls in the 12 months prior to study enrollment and more frequently used benzodiazepines concomitantly. The antidepressants most often used were paroxetine (34.6%) and amitriptyline (23.5%). The range of plasma concentrations were fluoxetine: <20 µg/L – 366 µg/L (fluoxetine + norfluoxetine), fluvoxamine: 126-330 µg/L, sertraline: <5 µg/L -91 µg/L, paroxetine: <5 µg/L -370 µg/L, (es)citalopram: <5 µg/L -174 µg/L, amitriptyline: <22 µg/L -77.7 ug/L (amitriptyline + nortriptyline), nortriptyline: <22 µg/L -329 µg/L. Median concentrations of the individual antidepressants did not differ significantly between fallers and non-fallers, both at baseline and follow-up (Supporting information Table S1). Insupporting information Table S2 present an overview of the reference values for therapeutic and (potential) toxic concentrations. Paroxetine, (es)citalopram plasma concentrations were in therapeutic range, but relatively low. Sertraline and amitriptyline plasma concentration were below therapeutic range. Nortriptyline plasma concentrations were higher in fallers compared to non-fallers (non-significant) and at follow-up above therapeutic range.