Samuel J Tromans, Helen Neilens, Crispin Musicha, Victoria Allgar, Emily Stanyard, Richard Laugharne, Paula McGowan, Angela Hassiotis, Sarah Lennard, Lance V Watkins, Bhathika Perera, Kiran Purandare, Ashok Roy, Indermeet Sawhney, Sujeet Jaydeokar, Ryan Ashford, Chris Rollinson, Hanna Abraham, Nusra Khodabux, Ogheneochuko Akusu, Samuel Paisley, Georgios Mousailidis, Meera Naran, Rohit Shankar
Our study suggests that converting antipsychotic doses to chlorpromazine units is a simple and effective way to understand and compare prescribing burden for PwID. It also facilitates measuring prescribing and implementing best practice.
BACKGROUND: In England and Wales, significant numbers of people with intellectual disability (PwID) are prescribed antipsychotics for a range of licensed and non-licensed indications, particularly behaviours that challenge. There is no system to compare antipsychotic prescribing practices across specialist adult intellectual disability (ID) services.
AIM: This study aimed to determine whether converting antipsychotics and their doses to equivalent chlorpromazine units enables comparison of licensed (psychosis, etc.) and non-licensed (behaviours that challenge) prescribing between different services.
METHOD: A feasibility retrospective cohort study using convenience sampling captured anonymized data of PwID on ⩾2 antipsychotics across eight specialist England and Wales adult ID services. The doses prescribed across 2017-2023 were converted to chlorpromazine-equivalent values, and antipsychotic dose burden across services was compared. Patients' characteristics and antipsychotic dosing are summarized descriptively. A mixed-effects regression model determines changes in chlorpromazine unit values across time. Subgroup analysis explores trends. Stata: Release 17 (StataCorp, 2021) and R (R Core Team, 2025) were used.
RESULTS: Of the 424 reviewed records, a higher proportion were male (ranging from 58% to 71% across census years) and white individuals (73%-85%). Autism (42%-58%), psychotic illness (61%-71%), and behaviours that challenge (77%-87%) were the most common comorbidities. Chlorpromazine units could be captured for 98% (n = 416). PwID with psychosis, behaviours that challenge, depression, or attention-deficit/hyperactivity disorder were prescribed significantly higher chlorpromazine-equivalent doses. Over 25% were prescribed more than 1000 mg/day chlorpromazine equivalent, which exceeds the British National Formulary-recommended maximum dose.
CONCLUSIONS: Our study suggests that converting antipsychotic doses to chlorpromazine units is a simple and effective way to understand and compare prescribing burden for PwID. It also facilitates measuring prescribing and implementing best practice.