Therapeutic drug monitoring of LAI antipsychotics as a predictor of clinical relapse: a one-year follow-up

INTRODUCTION: Clinical relapses in schizophrenia remain a frequent event. Long-acting injectable (LAI) antipsychotics enhance adherence, but low blood levels can sometimes be observed despite an adequate posology. Nonetheless, the evaluation of this parameter is uncommon in clinical practice. OBJECTIVES: To explore the potential advantages of therapeutic drug monitoring (TDM) of LAIs as a predictor of relapse in clinically stable outpatients with schizophrenia. METHODS: 44 individuals who had reached the pharmacokinetic steady state of LAI treatment (paliperidone, olanzapine, aripiprazole) underwent an anamnestic and psychopathological assessment. LAI blood levels were measured using liquid chromatography-mass spectrometry and classified as “in range” or “under range” according to the Arbeitsgemeinschaft für Neuropsychopharmakologie und Pharmakopsychiatrie (AGNP) guideline values. Individuals who relapsed during the one-year follow-up were compared to non-relapsers (Fisher’s exact test, χ(2) or Mann-Whitney U). An exploratory binary logistic regression tested the role of other possible relevant predictors of relapse. RESULTS: No differences were observed in baseline use of mood stabilisers (p=0.211), antidepressants (p=0.530), or prescribed LAI (p=0.563). Other comparisons are presented in the table: among these variables, in-range LAI levels were the only significant predictor of relapse (F=5.95, p=0.015; OR 0.04, 95%CI 0.02-0.56). CONCLUSIONS: TDM of LAIs may optimise the clinical management of schizophrenia by highlighting a suboptimal dosage and a consequent higher relapse risk. Large-scale, drug-specific assessments are needed to confirm these findings. DISCLOSURE: No significant relationships.