Efficacy of antipsychotics in delusional infestation.

BACKGROUND:Data remain scarce for the first-line antipsychotic choice in treating delusional infestation (DI). OBJECTIVES:We evaluated the treatment responses associated with different antipsychotics in DI patients. METHODS:We undertook a multicentre, retrospective observational study using anonymised electronic patient records from two hospitals in the United Kingdom from 1 January 2011 to 1 January 2023. Eligible participants were adults (≥18 years) diagnosed with DI treated with an antipsychotic, and had both an assigned baseline and follow-up Clinical Global Impression Scale (CGI-S) score. The CGI-S is a validated psychiatric research tool. Participants were excluded if they had known limited or non-adherence to an antipsychotic, or if no CGI-S scores were present at follow-up. First clinic visits before the initiation of an antipsychotic were assigned as the baseline CGI-S score. The last available CGI-S score before the patient either changed antipsychotic or left the clinic for any reason was used to assign follow-up CGI-S scores. The primary outcome was the response to each individual antipsychotic treatment, measured by the difference in the baseline and last available follow-up CGI-S scores. Differences in CGI-S changes between antipsychotic episodes were tested by analysis of variance (ANOVA). RESULTS:In total, 414 patient records were analysed, and data were extracted. The mean age was 61.8 years (SD 14.1). One hundred seventy (41%) of 414 patients were men and 244 (59%) were women. In total, 156 (38%) of 414 patients were eligible, yielding a total of 315 antipsychotic prescribing episodes. The ANOVA, ranking in order of treatment response, showed that the highest mean score (expressing highest treatment response) was observed in amisulpride (31 [67%] of 46) and risperidone (95 [57%] of 167), followed by some distance by quetiapine (9 [36%] of 25), aripiprazole (13 [28%] of 46) and olanzapine (7 [25%] of 28). CONCLUSIONS:Amisulpride and risperidone were associated with a higher treatment response than quetiapine, aripiprazole and olanzapine. Amisulpride and risperidone should therefore be considered the first-line treatment options in DI patients.