Links between the amount of antipsychotic medication prescribed per population at general practice level, local demographic factors and medication selection

Abstract

Background: Antipsychotic medications are the first-line pharmacological intervention for severe mental illnesses (SMI) such as schizophrenia and other psychoses, while also being used to relieve distress and treat neuropsychiatric symptoms in dementia. Our aim was to examine the factors relating to antipsychotic prescribing in general practices across England and how cost changes in recent years have impacted on antipsychotic prescribing.

Methods: The study examined over time the prescribing volume and prices paid for antipsychotic medication by agent in primary care. Monthly prescribing in primary care was consolidated over 5 years (2013-2018) and DDD amount from WHO/ATC for each agent was used to convert the amount to total DDD/practice. The defined Daily Dose (DDD is the assumed average maintenance dose per day for a drug used for its main indication in adults.

Results: We included 5750 general practices with practice population > 3000 and with > 30 people on their SMI register. In 2018/19 there were 10,360,865 prescriptions containing 136 million DDD with costs of £110 million at an average cost of £0.81/DDD issued in primary care. In 2017/18 there was a sharp increase in overall prices and they had not reduced to expected levels by the end of the 2018/19 evaluation year. There was a gradual increase in antipsychotic prescribing over 2013-2019 which was not perturbed by the increase in drug price in 2017/18. The strongest positive relation to increased prescribing of antipsychotics came from higher social disadvantage, higher population density (urban), and comorbidities e.g. chronic obstructive pulmonary disease (COPD). Higher % younger and % older populations, northerliness and non-white (Black and Minority Ethnic(BAME)) ethnicity were all independently associated with less antipsychotic prescribing. Higher DDD/general practice population was linked with higher proportion(%) injectable, higher %liquid, higher doses/prescription and higher %zuclopenthixol depot. Less DDD/population was linked with general practices using higher % risperidone and higher spending/dose of antipsychotic.

Conclusions: The levels of antipsychotic prescribing at general practice level are driven by social factors/comorbidities. We found a link between depot prescriptions with higher antipsychotic DDD and risperidone prescriptions with lower antipsychotic DDD. It is important that all prescribers are aware of these drivers / links.

Keywords: Antipsychotic; Demographic; General practice; Prescribing; Psychosis; Variations.

Fig. 1

Development of antipsychotic prescribing over 5 years including changes in drug cost. Q = quarter 1, 2, 3 or 4 of the year

Fig. 2

Multivariate regression describing the factors at a general practice level relating to antipsychotic prescribing. The length of the bars in Fig. 2 relates to the size of the standardised beta. The defined Daily Dose (DDD is the assumed average maintenance dose per day for a drug used for its main indication in adults. This is specific for each agent shown here