Factors associated with non evidence-based prescribing of antipsychotics

Non evidence-based prescribing of antipsychotics is common in the UK and internationally with high doses and polypharmacy the norm. These practices often remain even after systematic attempts are made to change. We aimed to establish which factors are linked to antipsychotic prescribing quality so we can identify and target patients for interventions to improve quality and allow us to understand further the drivers of non evidence-based prescribing.

A cross-sectional survey with a collection of factors potentially affecting antipsychotic prescribing quality outcomes was carried out in eight secondary care units in England. Participants were inpatients prescribed regular antipsychotics on the day of the survey. Antipsychotic dose, polypharmacy, type and route were the main outcome measures.

Data were collected for 1198 patients. Higher total dose was associated with greater weight, higher number of previous admissions, longer length of admission, noncompliance with medication and use of an atypical antipsychotic. A lower total dose was associated with clozapine use. Polypharmacy was associated with not being a patient at the South London and Maudsley NHS Trust centre, the subject having a forensic history, a greater number of previous admissions and higher total dose. Younger age, not being detained under a Mental Health Act section, atypical antipsychotic use and oral route were predictors of antipsychotic monotherapy. Atypical antipsychotic use was associated with oral route, higher total dose, being administered only one antipsychotic, having had fewer previous antipsychotics and no anticholinergic use. Use of the oral route was associated with not being sectioned under the Mental Health Act, atypical antipsychotic use, younger age, non-schizophrenia diagnosis, fewer previous admissions and a lower total dose.

In patients with chronic illness who are detained, heavier, noncompliant, not taking clozapine and on a depot antipsychotic, prescribers use larger doses and antipsychotic polypharmacy. We found that use of percentage of licensed maximum doses favours typical antipsychotics arbitrarily, and that high doses and polypharmacy are inextricably linked.