Therapeutic drug monitoring for improved psychopharmacotherapy in elderly patients

Introduction: Age-related changes in pharmacokinetics and pharmacodynamics and a higher prevalence of comorbidity and polypharmacy justify that therapeutic drug monitoring (TDM) is strongly indicated to increase the tolerability of psychopharmacotherapy in elderly patients. Geronto-TDM includes, additional to the classic TDM, several instruments which should increase the efficacy and safety of psychopharmacological treatment in the elderly. To improve safety, a risk-scale was developed to assess the risk of adverse drug reactions (ADRs) among psychiatric elderly inpatients.

Methods: Elderly inpatients ≥65 years were selected from TDM-requests and ADRs were assessed (UKU rating scale) retrospectively from medical files. The ADR risk-scale computed sum of risk-points (risk-score) for individual patients and compared the potential risk with observed ADRs.

Results: In total, 79 patients (65.8% female) with a mean (± SD) age of 73.5 ± 5.4 years could be included in the study. Mean calculated ADR risk-score was 5.3 ± 2.8. Amongst others, a significant association between supratherapeutic serum levels of the ingested psychotropic drug (χ2 = 7.66; p < 0.01; OR: 4.27, 95% CI: 1.47 – 12.38) and the occurrence of moderate to severe ADRs was found. The risk-score correlated significantly with the severity of observed ADRs. Spearman correlation coefficient was 0.582 (p < 0.01, CI 95%).

Conclusions: In clinical practice, TDM for elderly patients should monitor not only serum concentrations of drugs and psychopathology of patients but also the potential ADR-risk to support clinical decision-making. Amalgamation of TDM and objective risk scoring to Geronto-TDM will improve the safety of pharmacotherapy in gerontopsychiatry.