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Royal College of Psychiatrists' Research Unit, 83 Victoria Street, London SW1H 0HW
Oxleas NHS Trust
Royal College of Psychiatrists' Research Unit
Royal College of Psychiatrists' Research Unit
Imperial College School of Medicine
Queen Elizabeth Hospital
C.P. has very occasionally received speaker fees from Eli Lilly and Pfizer. Over the past year she has been involved with research projects funded by Novartis, Eli Lilly and Janssen-Cilag, but has not received any personal income from those projects. T.S. has been paid honoraria by numerous pharmaceutical companies for contributing to educational events. In 2000 he attended a meeting as a participant in an advisory board for Pfizer. The views expressed do not necessarily reflect those of the Royal College of Psychiatrists.
See editorial pp. 401-402, and pp. 414-420, this issue. 
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Abstract |
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A 1-day census, involving 3576 psychiatric in-patients prescribed anti-psychotic medication, was conducted as a prelude to a multi-centre audit. The aim was to explore the extent to which a number of patient variables explain antipsychotic polypharmacy and the use of high doses of these drugs.
RESULTS
Prescriptions of more than one type of antipsychotic drug were made for 50.5% of patients. Patient factors that influenced the probability of polypharmacy were: younger age, being male, detained under the Mental Health Act and on a rehabilitation or forensic ward, and a diagnosis of schizophrenia. The effect of ethnicity was not significant. Polypharmacy was the most powerful factor influencing the probability of being prescribed a high dose. Identified patient variables accounted for only 18% of the variance in dose prescribed.
CLINICAL IMPLICATIONS
The patient and clinician factors that account for the unexplained variance need to be identified.
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Introduction |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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Method |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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All patients prescribed an antipsychotic drug between midnight 20 July and midnight 21 July 1998 were included. Data were collected from prescription charts about the type, dose and route of administration of all antipsychotic drugs administered and/or prescribed during the census period. In addition, the age, gender, ethnicity, diagnosis (according to ICD-10; World Health Organization, 1992) and Mental Health Act (MHA) status of all 3576 patients were recorded together with the type of psychiatric bed that they occupied (acute, rehabilitation or forensic).
Data management
Data were returned to the Royal College of Psychiatrists' Research Unit and
analysed using SPSS for Windows, version 8.
Missing data
Age was not recorded for 55 subjects (1.5%), gender for 20 (0.6%),
ethnicity for 372 (10.4%), MHA status for 22 (0.6%) and diagnosis for 111
(3.1%). All valid cases were included in each analysis.
Data analysis
Thirty-one different antipsychotic drugs were prescribed for the patient
sample (22 oral preparations, 4 drugs in aqueous solution to be given
parenterally and 5 in longer-acting preparations to be given
intramuscularly).
Furthermore, many patients were prescribed more than one antipsychotic drug concurrently (see Results). For the regression analysis, the doses of these antipsychotic drugs had to be standardised and summed. The method used is described in an accompanying paper (Harrington et al, 2002a, this issue).
The probability of a subject being prescribed polypharmacy was modelled using logistic regression. The dependent variable was whether more than one antipsychotic drug was prescribed to be given during the 24-hour census period (yes/no). The independent variables (age, gender, ethnicity, MHA status, diagnosis and ward type) were entered individually and then in combination.
A second set of logistic regressions was performed with the dose of antipsychotic prescribed as the dependent variable (high dose/standard dose) and polypharmacy (yes/no) as a further independent variable. Linear regression was also carried out with the dose prescribed expressed as a continuous variable (percentage of British National Formulary (BNF; British Medical Association & Royal Pharmaceutical Society of Great Britain, 1999) maximum) and using the same explanatory variables.
Finally, the regression analyses were repeated using dose of antipsychotic medication actually administered as the dependent variable. That is, medication that was prescribed but not given during the census period was excluded from the analysis.
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Results |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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There were differences between groups within the sample. The mean age of
women was significantly higher than that of men (42.9 v. 39.0 years,
95%; CI of the difference=3.1-4.8; t-test, t=8.7,
P<0.001). Men were more likely to be formally detained than women
(54% v. 43%; 
2=37, P<0.001). Black and
Asian people and those from other ethnic minorities were younger than the
White people (36.1, 36.0 and 33.5 v. 41.0; Kruskal-Wallis,
2=71, P<0.001). A higher proportion of those from
the three ethnic minority groups were detained under the MHA than those who
were White (78%, 61% and 66% v. 47%; 2=120,
P<0.001).
Polypharmacy
Half of patients were prescribed more than one anti-psychotic drug
concurrently (50.5%; n=1807). The results of the logistic regression
for polypharmacy can be summarised as follows:
Doses of antipsychotics
Although 23.3% (n=832) of patients were prescribed a high dose,
this was actually administered to only 10.4% (n=371) during the
24-hour census period. The difference was almost entirely accounted for by
‘as required’ medication that was written on the prescription
chart but not given during the census period.
Effects of variables on dose of antipsychotics
Fewer than 1% of patients (n=34) were prescribed a single
antipsychotic drug at a dose that exceeded BNF limits. For the
remainder, high dose was owing to the effect of the concurrent prescription of
more than one antipsychotic. Thus, only 2% of the 1769 subjects prescribed a
single antipsychotic drug were prescribed a high dose compared with 44% of the
1807 subjects who were prescribed more than one antipsychotic drug. This
difference was highly significant (2=900,
P<0.0001).
The effects identified by the regression involving high dose can be summarised as follows:
The effects of each explanatory variable changed little after controlling for all the others, apart from age and gender, which became insignificant.
Using dose of antipsychotic actually administered as the dependent variable in the regression gave very similar results to that which used dose prescribed.
The linear regression, using prescribed dose expressed as a percentage of BNF maximum, yielded very similar results to the logistic regression analysis. Age, gender, ethnicity, MHA status, diagnosis and ward type in combination explained only 18% of the variance in high-dose prescribing. However, 40% of the variation was explained when polypharmacy entered the linear regression model along with these six other explanatory variables.
Differences between patients in different types of beds
Patterns of prescribing by bed type are given in
Table 1. Compared with acute
and rehabilitation wards, forensic wards had a higher proportion of patients
receiving high-dose antipsychotic medication, who were on depot
medications.
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Discussion |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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Being detained under the MHA approximately doubled the odds of being prescribed or receiving either more than one antipsychotic drug or a high dose. It could be argued that patients admitted compulsorily are more disturbed than those admitted informally. However, this argument is uncertain, given the current pressure on inpatient beds (Harrington et al, 2002b, this issue).
The results of this study highlight the need for further and more detailed examination of the patient characteristics that influence prescribing practice. Despite the significant contributions found for the explanatory variables measured in this study, together they explained less than a fifth of the variance in the combined dose of antipsychotic medication. Other characteristics of the patient that might account for some of this unexplained variance include: length of illness, history of relapse, level of disturbance, resistance of symptoms to antipsychotic medication and pharmacokinetic differences between individuals. Some of the variance might also be due to differences between clinicians (Wilkie et al, 2001) and/or the characteristics of the treatment setting. These factors are considered more fully elsewhere (Harrington et al, 2002b, this issue).
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Acknowledgments |
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References |
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BHUI, K. (1998) London's Ethnic Minorities and the Provision of Mental Health Services. In London's Mental Health: The Report to the London King's Fund Commission (eds S. Johnson, R. Ramsay, G. Thornicroft, et al), pp. 143-166. London: King's Fund.
BRITISH MEDICAL ASSOCIATION & ROYAL PHARMACEUTICAL SOCIETY OF GREAT BRITAIN (1999) British National Formulary. London & Wallingford: BMJ Books & Pharmaceutical Press.
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HARRINGTON, M., LELLIOTT, P., PATON, C. et al
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MUSCETTOLA, G., BOLLINI, P. & PAMPALLONA, S. (1991) Pattern of neuroleptic drug use in Italian Mental Health Services. Annals of Pharmacotherapy, 25, 296-301.[Abstract]
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WALKUP, J. T., McALPINE, M. A., OLFSON, M., et al (2000) Patients with schizophrenia at risk for excessive antipsychotic dosing. Journal of Clinical Psychiatry, 61, 344-348.
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WORLD HEALTH ORGANIZATION (1992) The ICD-10 Classification of Mental and Behavioural Disorders. Clinical Description and Diagnostic Guidelines. Geneva: WHO.
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| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| British Journal of Psychiatry | Advances in Psychiatric Treatment | All RCPsych Journals |
