Beyond Bridging: Oral Antipsychotic Overlap at 3 Months During LAI Treatment Signals High-Dose Prescribing in Outpatient Care

Background Oral antipsychotics are often continued after long-acting injectable (LAI) antipsychotics are established, which can push total exposure into high-dose antipsychotic therapy (HDAT). We evaluated this practice across two outpatient pathways. Methods Observational service evaluation of consecutive adults with psychotic disorders prescribed antipsychotics. LAI and oral use were recorded at baseline (t0). At 3 months (t3), we extracted the active regimen, concurrent dose burden (concurrent defined daily dose index [cDDD]), oral overlap (LAI+oral), and whether the regimen exceeded a prespecified study high-dose threshold (cDDD>1.5). Hospitalisation history was analysed with negative binomial regression. Results N = 58. At t3, 41/58 (70.7%) received an LAI and 22/58 (37.9%) had LAI+oral overlap; all overlap regimens exceeded the prespecified study high-dose threshold. Overlap was linked to higher cDDD. Higher cDDD, but not LAI status, was associated with more lifetime psychiatric hospitalisations. Conclusions At a standard 3-month review, continued oral overlap during LAI treatment was a simple marker of high-dose, high-burden prescribing and may serve as a practical audit checkpoint. This study did not assess whether overlap observed at month 3 persisted at later time points. Routine cDDD calculation and a clear stop/review plan for overlap may strengthen outpatient prescribing safety.