(312) Identifying Longitudinal Medication Adherence Patterns of Antipsychotic Treatments; A Real-World Cohort Study in Catalonia, Spain.

Background: Suboptimal medication adherence to antipsychotic treatments leads to worse therapeutic outcomes, particularly in people with severe mental health disorders. The adherence behaviour over time may be influenced by several factors including the number of antipsychotics used and their formulation.

Objectives: To identify longitudinal adherence patterns to oral and long-acting injectable (LAI) antipsychotics in monotherapy or polypharmacy through group-based trajectory modelling (GBTM).

Methods: Design/Setting: This was a retrospective cohort study that linked antipsychotic (ATC code: N05A) prescriptions and dispensing data from Catalonia, Spain. The study cohort included adults with a new prescription (90-day washout period) between 2016 and 2019. Data were obtained from the real-world databases of the Catalan public healthcare system (primary and secondary care).
Exposures or interventions: The antipsychotic therapeutic strategy was categorised according to the number of antipsychotic drugs (INN) (monotherapy/polypharmacy) and the formulation (oral/LAI) prescribed.
Main outcome: The response variable was percentage of adherence, estimated through the calculation of the continuous medication availability measure (CMA), in each 30-day period during 12 months of follow-up.
Statistical analysis: GBTM was used to identify clusters of individuals following a similar longitudinal trajectory of adherence. Model selection was guided by model fit criteria and the clinical relevance of the trajectories. Identified trajectories were compared in their baseline and treatment characteristics: therapeutic strategy, polypharmacy characteristics, previous antipsychotic exposure, and prescriber specialty.

Results: Among the 7,730 people included in the study, we identified seven clinically distinct trajectory groups that best described our sample: “non-adherent” (19%), “low adherent” (9%), “early-decline” (6%), “mid-decline” (5%), “late-decline” (5%), “high adherent” (21%), and “fully adherent” (35%). Trajectories with better adherence were more likely to receive the prescription from a psychiatrist, receive LAI and have previous exposure to other antipsychotics. Intermittent medication use patterns and high levels of polypharmacy were characteristics of both the low and high adherent groups.

Conclusions: The trajectories reflect three different adherence behaviours: stable adherence over time (fully adherent or non-adherent); patients who discontinue treatment at some point and; patients with an intermittent refill pattern. Interventions should be specifically designed to target each behaviour that leads to a suboptimal adherence outcome and LAI should be considered, as they appear to be associated with better adherence