The relevance of TDM for long-acting injectable antipsychotics

Introduction Pharmacoepidemiological data suggest an emerging prescription trend for second generation antipsychotics including long-acting injectable (LAI) formulations. Further, the use of therapeutic drug monitoring (TDM) as part of clinical routine of treatment with LAI antipsychotics receives increasing attention. We systematically reviewed available TDM evidence during the switch from the oral formulation to the LAI counterpart as well as in the LAI maintenance treatment.

Methods Available TDM studies for LAI antipsychotics can be classified as follows: 1) positron emission tomography (PET) findings regarding dopamine (D₂/D₃) receptor occupancy related to LAI antipsychotic blood levels, 2) TDM studies on the transition from oral to LAI antipsychotics and 3) TDM data from patients receiving maintenance treatment with LAI formulations.

Results Demographic characteristics, such as age and sex, genetic peculiarities affecting metabolizer status and clinical variables including co-medications and co-morbidities may crucially impact LAI antipsychotic blood levels. A trend towards lower concentrations under LAI compared to oral antipsychotics was observed implying the need to adapt therapeutic reference ranges for some LAI antipsychotics adopted from their oral counterparts.

Conclusion Available TDM evidence suggest varying bioavailability patterns for newer LAI antipsychotics, essentially captured with the use of regular TDM. Thus, we recommend using TDM when switching an antipsychotic from oral to its LAI formulation as well as during dose selection.

Conflict of Interest GS has served as a consultant for HLS Therapeutics and Thermo Fischer.

Publication History

Article published online:
16 May 2022