Background: Antipsychotics are key for treating severe mental illnesses, and they are usually prescribed in different dosages for long-term periods. Although high exposure to these drugs is associated with chronic diseases development (e.g., cardiovascular diseases), little is known about how antipsychotics are prescribed in real-life contexts.
Objectives: To describe antipsychotic dose patterns and how these vary across groups by age, gender, and social deprivation up to 13 years from the first prescription.
Methods: Retrospective cohort study using UK primary care data (The Health Improvement Network). We evaluated individuals aged 18 to 99 between 2006 and 2018, observed from the first prescription date of olanzapine, risperidone, quetiapine, and haloperidol up to 1 (short term) and 13 years (long term). We used the NICE criteria to define the dose level of each prescription record (1 = low, 2 = high intensity). For each three months of individual follow-up (quarter), we selected the highest dose recorded to define the dose of that period. Then, we described short-term dose change with Sankey plots and performed a latent class growth analysis to identify clusters of patients with different long-term dose patterns, overall and stratified by socio-demographics.
Results: In total, 27,876 individuals were included in the study: 13,359 men (47.9%) and 14,517 women (52.1%). There were 53.0% prescribed high dose at quarter 1 (Q1), and 36.2% prescribed high dose at Q4 (short term). In general, men were prescribed higher doses than women (Men: Q1: 58.3%; Q4: 39.5%; Women: Q1: 48.2%, Q4: 33.2%). Younger people were also prescribed higher doses than older people (18-65 years: Q1: 62.7%, Q4: 42.0%; 65-99 years: Q1: 23.1%, Q4: 18.0%). Most deprived people were more exposed to high doses than those least deprived (Most deprived: Q1: 58.3%, Q4: 41.9%; Least deprived: Q1: 47.5%, Q4: 30.2%). We detected six clusters according to prescription patterns: four clusters of people who -mostly- started on high doses, changing to low over time and eventually stopping these antipsychotics at years 1, 2, 4 and 7 (41.0%, 20.7%, 14.4% and 9.1% people respectively), one cluster keeping high dose up to year 10 (5.3%), and one cluster keeping low dose up to year 8 (9.5%).
Conclusions: Men, younger and most deprived people with severe mental illnesses are more exposed to high doses of antipsychotics in the first year of treatment. High exposure reduces over time in the same period. In the long term, most people had moderate exposure (⁓60% with dose reduction and exposure < 3 years), while the rest varied from moderate to high exposure between 4 and 10 years.
