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Brent East Sector, 13-15 Brondensbury Road, London NW6 6BX; tel: 020 8937 6329; fax: 020 8937 6333
Research Psychiatric Rehabilitation Services, Fremantle Hospital and Health Services, PO Box 480 Fremantle, Western Australia 6160, Australia
Barnet Hospital
Correspondence: e-mail: alcuin{at}alc-jean.demon.co.uk
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Abstract |
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 Top Abstract IntroductionMethodResultsDiscussionReferences |
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Neuroleptic medication is often used in excess of the BNF maximum. The purpose of this study was to examine the relationship of neuroleptic dose to patient, prescriber and environmental factors, by using a cross sectional ‘snapshot’ study of psychiatric in-patient prescriptions combined with a retrospective case note survey.
RESULTS
It was found that certain consultants prescribe higher doses of neuroleptics than others. Patients with a history of aggression had a nine and a half times higher chance of being prescribed higher doses of neuroleptics. Patients with a greater than 5-year history of neuroleptic prescription received higher doses.
CLINICAL IMPLICATIONS
High neuroleptic prescription is related more to patients' past reputation and prescriber differences than to patients' current behaviour.
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Introduction |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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There are significant differences in the pharmacokinetics and pharmacodynamics of neuroleptics between individuals (Ko et al, 1985; Van Tol et al, 1992) and across ethnic groups (Lin et al, 1995) — such that different people given the same oral dose will have widely differing blood levels of the drug and will respond differently. Response to neuroleptics is invariably measured according to subjective symptoms and signs, and there are no objective patient indicators to guide dose ranges for neuroleptic prescribing. For these reasons there is no clear relationship between neuroleptic dose and clinical response (Baldessarini et al, 1988), and more scope for variation in dose to relate to prescriber habits. The few studies that have examined the relationship of neuroleptic dose to prescriber, environmental and patient history variables demonstrate an association of higher neuroleptic dose with a history of violence; recent disruptive or violent behaviour; treatment non-responsiveness; and longer duration of admission (Krakowski et al, 1993; Chaplin & McGuigan, 1996; Peralta et al, 1994). These studies suggest higher dose prescription relates more to patients' history than to current variables such as age, weight, diagnosis or mental state. We examined the relationship between total neuroleptic prescribing and high dose neuroleptic prescribing against relevant patient and prescriber variables for all patients at a psychiatric hospital that had acute, rehabilitation and forensic patients.
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Method |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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Chi-squared (
2) analysis and analysis of variance were used
to examine the relationship of the above variables to above and below
BNF maximum prescribing and to chlorpromazine equivalent dose,
respectively.
A stepwise logistic regression analysis was used entering aggression variables first including history of aggression; current verbal aggression, current physical aggression and 5-year history of neuroleptic prescription, the second step included entering current absconding and other current negative behaviour and self-harm. The predictor variables were regressed on, high v. low chlorpromazine equivalent patients. Cases were selected at the 75 percentile (1462 mg) to include 50 patients for the high chlorpromazine equivalents and the low, at the 25 percentile (400 mg) was represented by 56 patients. The same predictors were also used for above v. below BNF maximum dose cases. In the case of above BNF maximum dose, a random selection of below BNF maximum patients were matched to the above BNF maximum cases. The unique contribution of each predictor was observed in order to reduce type one error susceptibility with multiple univariate comparisons. Cell sizes for each group of high v. low chlorpromazine dose and above v. below BNF prescription were large enough to meet statistical power for each regression procedure (Tabachnick & Fidell, 1989). All tests were conducted using SPSS for Windows (Norusis, 1994).
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Results |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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Univariate analyses
Setting was divided into acute wards (n=86, 42.6%), rehabilitation
wards (n=71, 35.1%) and forensic wards (n=45, 22.3%). There
was a highly significant difference between consultants in chlorpromazine
equivalents prescribed (F=3.61; df=201; P=0.0002). Post hoc
analysis revealed that one forensic consultant prescribed significantly higher
chlorpromazine equivalent doses than eight of the other 10 consultants. This
consultant gave rise to a significantly higher chlorpromazine equivalent
prescribing in the forensic compared to the acute setting (F=5.15;
df=201; P=0.007), which disappeared when this consultant was removed
from the comparison between settings.
Differences were observed between the two consultants within the
rehabilitation setting for both above BNF (2=4.38;
df=1; P=0.036) and chlorpromazine equivalents prescription
(F=10.1; df=71; P=0.002), revealing that one rehabilitation
consultant prescribed consistently higher than the other consultant despite
similar patient numbers and profile.
The UK Office of Population Censuses and Surveys categories were collapsed into White, n=146 (72.3%), Black African or Caribbean, n=33 (16.3%), and other, n=23 (11.3%). No interaction effect was observed between ethnicity and chlorpromazine equivalent dose, nor did it discriminate between above and below BNF classifications.
Analysis of variance revealed a significant difference between diagnostic groups, with schizophrenia and other psychoses having higher average chlorpromazine doses prescribed (F=2.53; df=200; P=0.02).
Of the 202 patients 25 were on as required benzodiazepines and 13 on regular benzodiazepines. Neither of these categories contributed to any significant difference in chlorpromazine equivalent prescription.
Multivariate analyses
The stepwise logistic regression model for the above and below BNF
maximum classifications did not significantly improve the constant with the
classification table not providing above chance results (see
Table 2). History of aggression
was a significant predictor in the first block of variables
(P<0.05). The other current behaviour variables did not contribute
to above and below BNF dose classification.
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In the stepwise logistic regression model for high v. low
chlorpromazine dose the first group of variables significantly contributed to
the classification (2=34.15, P<0.0001) with
history of aggression (P<0.001) and history of 5-year neuroleptic
prescription (P<0.05) being significant predictors (see
Table 2). When the second block
of variables were entered into the equation they did not improve the fit of
the model observing a non-significant 2 result. The
classification results demonstrated the 70% of high and 82% of low
chlorpromazine equivalent patients being correctly classified with an overall
classification of 76%.
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Discussion |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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At the time of the study 20% (41/202) of in-patients on neuroleptics were prescribed at or above BNF maximum, indicating that it is not uncommon for patients to be prescribed at or above the top of the therapeutic range, particularly when forensic and rehabilitation patients are included in the sample.
This study demonstrates the importance of individual consultants in determining neuroleptic prescription. This is supported by two results. First, one consultant was found to prescribe significantly higher chlorpromazine equivalence than eight of the other ten consultants. This cannot be explained merely by a difference in this consultant's case-load because despite the fact this consultant was prescribing in a forensic setting, the allocation of patients to the four forensic consultants was random. When this consultant was taken out of the analysis the difference between the forensic and acute settings became non-significant, indicating this consultant's prescribing habits were solely responsible for the observed difference between the forensic and acute settings. Second, within the rehabilitation setting one consultant prescribed consistently more both in terms of above BNF maximum and chlorpromazine equivalents, despite both consultants having demographically and diagnostically equivalent case-loads.
Ethnicity did not contribute to differences in neuroleptic prescription. It has been suggested that Black patients are medicated to a higher degree than White patients (Strakowski et al, 1993) — this study found no evidence to support this. Unlike an earlier study (Krakowsi et al, 1993) we did not demonstrate an effect of length of admission on neuroleptic prescription, but noted a significant but small contribution of increased age and length of illness to higher chlorpromazine equivalent prescription. This may relate to the possibility that as a psychotic illness progresses, neuroleptic dose is frequently increased by a succession of different doctors, but is less often reduced — on the basis that ‘they must be on that dose for a good reason’. Having age and length of illness as significant predictors for chlorpromazine equivalent prescription indicates that patients accumulate higher doses of medication as an index of time rather than the severity of their illness.
The logistic regression clearly confirmed previous findings that history of violence predicts higher neuroleptic prescription (Krakowski et al, 1993; Chaplin & McGuigan, 1996), but did not demonstrate any contribution of disturbed behaviour during the last week on neuroleptic prescription, unlike previous studies (Krakowski et al, 1993; Chaplin & McGuigan, 1996; Peralta et al, 1994). This suggests that patients' reputation and history influences neuroleptic prescription far more than their current presentation. The only other significant predictor of high neuroleptic prescription was a positive history of larger than 5-years' neuroleptic prescription. Again this supports the notion that over time the dose of neuroleptic is frequently increased to limit patients' undesirable behaviour and is not then subsequently lowered for fear of the behaviour returning, as previously suggested (Van Putten et al, 1992). An alternative explanation is that patients with longer illnesses are on higher doses because there was a previous trend to prescribe higher doses, which they have remained on. If this was the case it still supports the argument that regular review and education of neuroleptics does not occur.
In summary this study shows three things: certain consultants prescribe higher doses of neuroleptics than others; patients with a history of aggression get prescribed higher doses of neuroleptics; and third, patients who have been on neuroleptics longer than 5 years get prescribed higher doses. As our study did not look at patients over time it is possible that patients with a history of aggression had previously not responded to lower doses of neuroleptics and subsequently responded to higher doses. However, the alternative explanation is that psychiatrists are prescribing on the basis of prejudice relating to patients' previous behaviour, if this is true — then who are we treating?
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References |
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TopAbstractIntroductionMethodResultsDiscussionReferences |
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| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| British Journal of Psychiatry | Advances in Psychiatric Treatment | All RCPsych Journals |
