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Royal College of Psychiatrists' Research Unit, 83 Victoria Street, London SW1H 0HW
Oxleas NHS Trust, Bexley Hospital
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, Ely 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 contributions 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. 411-418, this issue. 
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Abstract |
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 Top Abstract IntroductionMethodResultsDiscussionReferences |
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A 1-day census provided an opportunity to examine the variation between 44 mental health services in the frequency of prescribing high doses and polypharmacy of antipsychotic drugs to in-patients on acute psychiatric wards.
RESULTS
The proportion of patients prescribed a high dose ranged 0-50% and simultaneous use of more than one antipsychotic drug ranged 12-71%. A number of case-mix variables explained 26% and 40%, respectively, of the variance between services on these two indicators of prescribing practice.
CLINICAL IMPLICATIONS
Services with high rates of prescription of high dose or polypharmacy might consider a review of clinical practice and of service-level factors that might affect prescribing.
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Introduction |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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There is a consensus among English-speaking countries in the developed world that high doses or polypharmacy of antipsychotic drugs should be avoided, other than in exceptional circumstances (Harrington et al, 2002, this issue). A 1-day census of prescribing provided an opportunity to describe variation between UK mental health in-patient services and the extent to which this guidance is followed.
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Method |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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Data analysis
For each patient, prescribed antipsychotic medication was classified as
either standard dose or high dose, as defined in the associated paper by
Harrington et al
(2002, this issue). The unit of
analysis was the mental health service. For each service, the percentage of
patients in acute wards who were on a high dose of an antipsychotic or
polypharmacy was calculated. These percentages were then used as the dependent
variable in linear regression analyses to examine how much of the variation
between services could be explained by ‘case-mix’ factors that
were known to influence prescribing
(Lelliott et al, 2002,
this issue). These independent variables were mean age, proportion of patients
who were male, proportion detained under the Mental Health Act (MHA) and
proportion with a diagnosis of schizophrenic or delusional disorder. Although
ethnicity had been found not to influence the probability of being prescribed
a high dose or polypharmacy, the proportion of patients who were Black or from
an ethnic minority group was also included. Independent variables were entered
into the regression analysis individually and then in combination.
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Results |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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Variation between services
The mean number of eligible patients per service was 49 (range 20-126).
Services varied greatly in the proportion of patients who were prescribed high
doses (0-50%) and in the proportion on polypharmacy (12-71%). The natures of
the distributions are shown in Figs
1 and
2. The extent of variation
remains when services with relatively small sample sizes are removed. For the
24 services that included more than 40 patients, the proportion prescribed a
high dose ranged 8-50% and the proportion prescribed polypharmacy 26-71%.
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The effect of case mix
Table 1 shows the extent of
variation in case-mix variables between the patient cohorts from the 44
services.
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Effect on high-dose prescribing
The independent variables were first entered separately into a regression
analysis, with percentage of patients on a high dose as the dependent
variable. There were effects for the proportion detained under the MHA
(coefficient=0.37, P<0.01) and the proportion with a diagnosis of
schizophrenic or delusional disorder (coefficient=0.34, P<0.01).
However, when entered simultaneously, none of the individual predictor
variables had a significant effect. The model accounted for 26% of the
variance.
Effect on polypharmacy
In the multiple regression analysis with percentage of patients on
polypharmacy as the dependent variable, and independent variables entered
separately, significant predictors were the proportion of detained patients
(coefficient=0.54, P<0.001), the proportion with a diagnosis of
schizophrenic or delusional disorder (coefficient=0.44, P<0.01)
and the proportion of patients who were Black or from an ethnic minority
(coefficient=0.26, P<0.01). When variables were entered
simultaneously, the effect of proportion of detained patients remained
significant (standardised coefficient=0.41, P<0.05) and there was
also a non-significant trend for the percentage of patients from ethnic
minorities (coefficient=0.28, P<0.01). The model predicted 40% of
the variance.
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Discussion |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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The data collection method might have exaggerated the extent of
variation
This is either due to the small number of patients included by some
services or because of selection bias whereby services that participated were
able to decide which wards to include. However, the variation between services
remains, even after those with smaller patient samples are removed. Only
repeated censuses or continuous data collection over a period of time could
determine how ‘stable’ this variation is; that is, whether there
are services where a high proportion of patients are consistently prescribed
high doses and polypharmacy.
Some of the variation is due to differences in case-mix
Simple measures of difference between the patient groups in different
services did explain just over a quarter of the variance between services in
prescribing of high doses and 40% of the variance in polypharmacy. Variables
that most strongly affected prescribing were those most closely related to
severity of disorder — the proportion of patients with a schizophrenic
or delusional disorder and the proportion detained under the MHA. Perhaps if
other and better measures of severity had been included, more of the variance
might have been explained. Relevant measures might include length of illness,
severity of symptoms and disability, level of agitation or perceived
dangerousness, or treatment resistance.
A variety of factors unrelated to the patient might account for some
of the unexplained variation
It is possible that the prescribing style of individual psychiatrists might
have contributed to the variation between services. However, the identity of
the prescriber was not recorded and it is highly likely that, for all
services, the data reflect the prescribing of more than one consultant
psychiatrist and the supervised practice of more than one trainee
psychiatrist. This suggests that other service-level factors also need to be
considered. Differences in ward design, staffing levels, bed numbers and
access to a locked ward or intensive care area might affect the extent to
which very ill or disturbed patients can be managed without resorting to high
doses of medication.
In short, the findings of this survey pose more questions than they answer. They do, however, provide a ‘benchmark’ against which other services can compare themselves. Each incident of high-dose prescribing or polypharmacy should probably be audited for whether it is justifiable. Furthermore, services where these prescribing practices are consistently at the upper end of the ranges shown in Figs 1 and 2 might consider a wider review of prescribing practice and of service-level factors that might affect it.
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References |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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HARRINGTON, M., LELLIOTT, P., PATON, C., et al
(2002) The results of a multicentre audit of the prescribing of
antipsychotic drugs for in-patients in the UK. Psychiatric
Bulletin, 26,
414-418.
LELLIOTT, P., PATON, C., HARRINGTON, M. et al
(2002) The influence of patient variables on polypharmacy and
combined high dose of antipsychotic medication prescribed for in-patients.
Psychiatric Bulletin,
26,
411-414.
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