Plasma concentrations of citalopram in inpatients with acute major depression are predictive for later non-response. Data from an observational study

Introduction: Evidence has been given for citalopram that serum concentrations of at least 50 ng/ml are required to attain appropriate clinical improvement. We investigated if plasma concentrations of citalopram below 50 ng/ml on day 7, are predictive for non-response after 5 weeks of treatment in depressed inpatients. Material and Methods: Inpatients with a major depressive disorder according to ICD-10 were included and treated with citalopram. Psychopathology was assessed by the 17-item Hamilton Depression (HAMD-17) rating scale in weekly intervals for five weeks. In parallel, serum concentrations of citalopram were measured. Results: 55 patients were included (27 f). 84% of the patients with citalopram plasma concentrations below 50 ng/ml (n = 36) were non-responders at week five. Among patients who achieved plasma concentrations ≥ 50 ng/ml (n = 19) on day 7, 47% became responders at week five (p = 0.025) with a sensivity of 75% and a specifity of 60%, respectively. Predictive power for later non-response indicated for plasma levels below 50 ng/ml on day 7, an odds ratio (OR) of 4.5 (95% CI: 1.3–15.8). Conclusion: Our results revealed that plasma concentrations of citalopram below 50 ng/ml are predictive for later non-response.