Prescribing of antipsychotics for people diagnosed with severe mental illness in UK primary care: A 20-year investigation of who receives treatment, with which agents, and at what doses

Abstract

Background Contemporary data relating to antipsychotic prescribing in UK primary care for patients diagnosed with severe mental illness (SMI) are lacking. Aims To describe contemporary patterns of antipsychotic prescribing in UK primary care for patients diagnosed with SMI. Methods Cohort study of patients with an SMI diagnosis (i.e., schizophrenia, bipolar disorder, other non-organic psychoses) first recorded in primary care between 2000-2017 derived from Clinical Practice Research Datalink. Patients were considered exposed to antipsychotics if prescribed at least one antipsychotic in primary care between 2000-2019. We compared characteristics of patients prescribed and not prescribed antipsychotics; calculated annual prevalence rates for antipsychotic prescribing; and computed average daily antipsychotic doses stratified by patient characteristics. Results Of 309,378 patients first diagnosed with an SMI in primary care between 2000-2017, 212,618 (68.7%) were prescribed an antipsychotic between 2000-2019. Antipsychotic prescribing prevalence was 426 (95% CI, 420-433) per 1,000 patients in the year 2000, reaching a peak of 550 (547-553) in 2016, decreasing to 470 (468-473) in 2019. The proportion prescribed antipsychotics was higher amongst patients diagnosed with schizophrenia (81.0%) than with bipolar disorder (64.6%) and other non-organic psychoses (65.7%). Olanzapine, quetiapine, risperidone, and aripiprazole accounted for 78.8% of all prescriptions. Higher mean olanzapine equivalent total daily doses were prescribed to patients with the following characteristics: schizophrenia diagnosis, ethnic minority status, male sex, younger age, and greater deprivation. Conclusions Antipsychotic prescribing is dominated by olanzapine, quetiapine, risperidone, and aripiprazole. Two thirds of patients with diagnosed SMI were prescribed antipsychotics in primary care, but this proportion varied according to SMI diagnosis. There were disparities in both receipt and dose of antipsychotics across subgroups - further efforts are needed to understand why certain groups are prescribed higher doses and whether they require dose optimisation to minimise side effects.