Cost-effectiveness potential of therapeutic drug monitoring for depressed inpatients treated with citalopram by shortening of hospitalization

Introduction: Therapeutic drug monitoring (TDM) has been shown to enhance treatment efficacy and drug tolerability for many psychoactive drugs. Objective: The aim of this post hoc analysis of depressed inpatients treated under naturalistic conditions with citalopram was to evaluate the cost effectiveness potential of TDM. Methods: Patients were classified into two groups, one with plasma concentration below and one with plasma concentrations above 50ng/ml, which is the lower threshold level of citalopram's therapeutic reference range. Cost effectiveness was calculated by considering costs for hospitalization and costs for drug analysis. Between groups cost for hospitalization, medication costs and number of comedication were calculated and compared. Results: The study included 55 inpatients with major depression according to ICD-10 who were treated with citalopram. For patients with high citalopram plasma concentrations, the mean duration of hospitalization was 49±20 days, and it was 72±37 days in the group with low drug concentrations (P=0.03). Based on daily costs for hospitalization of 250€, the by mean 23 days shorter period of hospitalization amounted to 5,750 € savings per patient. This is by far higher than costs of 210 to 1,400 € that are billed in case of weekly plasma concentration monitoring. In the groups with high and low plasma concentrations, daily costs for citalopram medication were 3.00±0.80 and 2.42±0.70 €, respectively (p=0.002), and the mean number of comedications was 1.3 and 1.8 drugs, respectively (p=0.332). Conclusion: Our data indicate that TDM guided dosing of citalopram has an enormous potential to be cost effective by reduction of the duration of hospitalization.