5PSQ-122 Sequential change of dosing interval of paliperidone palmitate based on plasma concentration monitoring

Background and Importance Paliperidone is an antipsychotic used for the treatment of schizophrenia. To increase adherence to treatment and thus reduce the risk of relapse, it was formulated as an extended-release injectable. There are 3 types of formulations: monthly, quarterly and semi-annually. Monitoring of paliperidone plasma concentrations can help to optimise treatment, as patients who do not require dose adjustments may benefit from the longer therapeutic interval formulations (quarterly and semi-annual) Aim and Objectives To analyse the relationship between the change of presentation of paliperidone palmitate and its pharmacokinetic monitoring Material and Methods Retrospective observational study in which all patients whose plasma concentrations of paliperidone were determined from January to July 2023 were included. Patients on treatment with oral paliperidone were excluded. The variables collected were sex, age, current plasma concentrations of paliperidone palmitate, type of paliperidone palmitate formulation used in current treatment, initiation of paliperidone palmitate, presence of previous controls of another type of paliperidone palmitate formulation, previous plasma concentrations of paliperidone palmitate. Results Sixty-nine patients were included, 69.6% male with a median age of 50 years (20–72). Of the patients, 42.0% had plasma paliperidone palmitate concentrations within the therapeutic range. Of the patients, 36.3% were on paliperidone palmitate monthly, 42.0% were on paliperidone palmitate quarterly, and 21.7% were on paliperidone palmitate semi-annually. A change of paliperidone palmitate presentation had occurred in 87.0% of the patients. Of these, only 43.3% had pharmacokinetic monitoring prior to the change of presentation. Of these patients, 46.2% had plasma concentrations in range in the control with the previous presentation of paliperidone palmitate. Conclusion and Relevance Although the pharmacokinetic determination of plasma concentrations of paliperidone palmitate allows individualising the treatment to each patient, the decision to switch from one formulation of injectable paliperidone palmitate to another with a different dosing interval was not based on the plasma concentrations of the drug in our population. References and/or Acknowledgements Conflict of Interest No conflict of interest.