Antipsychotics Prescribing and Ethnicity

    Student thesis: Doctoral ThesisDoctor of Philosophy


    Treatment of mental illness differs between races. Many reports, investigations, public enquiries and surveys have been conducted documenting differences in referral to specialist mental health services, admission rates to hospital, detention under the Mental Health Act and seclusion whilst in hospital. These differences are particularly marked for black patients compared with white.
    Concerns about these differences, in addition to research (predominantly from the United States) showing differences in prescribing of antipsychotics for ethnic minorities, have prompted United Kingdom studies investigating any prejudicial prescribing of antipsychotics. Identified differences include use of high doses, more frequent use of older drugs and depot formulations, especially for black compared with white patients. Most of these UK studies were older, had small sample sizes and controlled for few, if any, confounding factors affecting antipsychotic prescribing. A large, multi-centre, cross-sectional survey of antipsychotic prescribing by ethnicity, collecting over 20 potential confounding factors, was undertaken to measure dose, high dose, polypharmacy, type of antipsychotic, cost of antipsychotic, clozapine use and route of administration. The null hypothesis was that black patients receive antipsychotic drug treatment of equal dose, type, number, cost and route to white patients. Data were analysed (using regression methods) for black and white patients alone (as these are the two ethnicities with the most reported differences in medication use), for all ethnicities (to see if any differences for other ethnic groups not only black and white), by individual centre (to determine if prescribing by ethnicity differs by location) and also to determine which factors predicted outcomes. Medical prescriber attitudes to prescribing by ethnicity were assessed using a case vignette and questionnaire method.
    Analysis by ethnicity did not find differences between black and white patients (n=938) in dose (adjusted percentage difference 0.97 [95% confidence interval (CI) -4.28, 6.22], p=0.72); high dose (adjusted odds ratio [AOR] 0.98 [CI 0.63, 1.51], p=0.92); use of first generation antipsychotics (AOR 1.25 [CI 0.87, 1.79], p=0.22); polypharmacy prescribed (AOR 1.15 [CI 0.87, 1.51], p =0.33); polypharmacy administered (AOR 1.08 [CI 0.78, 1.49], p=0.66); or cost of antipsychotic treatment (adjusted effect size 1.75 [CI -9.81, 13.31], p=0.77). Re-analysis including all ethnicities and inclusion of two other outcomes (route of administration and clozapine use), also did not find differences by ethnicity although many variables were associated with the outcomes. Some of these relationships were unexpected, for example the use of lower doses and first generation antipsychotics, but most could be explained rationally.
    Analysis of data by the different sites involved revealed differences in prescribing by ethnicity, particularly for one centre. These effects included higher doses, polypharmacy, greater use of 1st generation antipsychotics and higher costs predominantly for black compared with white patients. Unfortunately for some of these outcomes it was not possible to adjust results for potential confounders because of some centres’ small sample sizes and missing data.
    After dissemination of findings, ethnic minority prescribers reported that they were very surprised with the results of these studies on antipsychotics and ethnicity. They said they purposely prescribed higher doses for black patients as they were more severely ill on admission to hospital. To test the validity of these comments all medical prescribers at one NHS trust were surveyed using a case vignette and questionnaire. Differences were not found in antipsychotic prescribing by ethnicity for percentage maximum dose (47.7% black, 50.9% white, p=0.57), high dose (1.67% black, 3.33% white, p=0.68), type (1.6% black, 2.5% white, p=0.10), polypharmacy (3.3% black, 6.5% white,
    p=0.37) and route of administration (intramuscular 0.8% black, 0% white; oral black 44.7%, white 45.5%; oral or intramuscular black 3.3%, white 5.7%; p=0.53) outcomes.
    The study was, at the time it was undertaken, the largest UK study of antipsychotic prescribing in black and white patients and the most geographically diverse. Overall clinical and theoretical studies described in this thesis did not show differences in antipsychotic prescribing by ethnicity. Some individual centres may have poorer prescribing by ethnicity that requires remedial action, although such differences were infrequently observed. Nevertheless, for all of these studies significant limitations, including in design and analysis, may have affected these results.
    Date of Award2018
    Original languageEnglish
    Awarding Institution
    • King's College London
    SupervisorDavid Taylor (Supervisor) & Graham Davies (Supervisor)

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