ANTIPSYCHOTIC DRUG DOSES IN A SCHIZOPHRENIA INPATIENT UNIT Cherrie A. Galletly

Dose-effect studies have found that 600 mg/day of chlorpromazine (or its equivalent) is generally sufficient to treat acute psychosis. This paper reports on the doses of antipsychotic medication prescribed for inpatients in a Schizophrenia Unit at an Australian state hospital. Fifty five percent of patients received daily doses equivalent to more than 600 mg of chlorpromazine and 26% received daily doses equivalent to more than 1500 mg of chlorpromazine. Low potency drugs were prescribed in lower doses than high potency drugs. Patients prescribed depot medication tended to receive higher doses of medication than those prescribed oral medication only. Australian and New Zealand Journal of Psychiatry 1992; 26574-576 Antipsychotic drugs have a high incidence of doserelated side effects, including sedation, extrapyramidal symptoms and tardive dyskinesia, so it is important that the minimum effective dose is prescribed. A review of dose-effect studies [ I ] concluded that moderate doses (500-600 mg/day of chlorpromazine or its equivalent) were usually sufficient to treat acute psychosis, with higher doses generally producing little additional improvement. Radioligand binding studies [2] found that a good treatment response could be obtained with a 65-85% occupancy of central D2-dopamine receptor sites, achieved with daily doses equivalent to 80-400 mg of chlorpromazine. Surveys of antipsychotic drug doses undertaken in the USA [3-51 reported that many patients were prescribed doses well above these levels, particularly if high potency drugs were used. However, the only survey of large numbers of patients [3] was restricted

to oral drugs. Inderbitzin et a1 [4], in a study of 40 patients, compared doses of depot and oral antipsychotic drugs, and concluded that higher doses of depot drugs were prescribed. This study has been criticised [6,7] for the use of a conversion formula equating 25 mg/2 weeks of fluphenazine decanoate with 1500 mg/day of oral chlorpromazine, which may have produced spuriously high fluphenazine decanoate doses. Reardon et a1 [5] demonstrated an increase in antipsychotic drug doses over the decade 1973- 1982. They found that re-analysis of their data excluding patients receiving depot drugs gave essentially similar results. Inderbitzin era/ [4] comment on the lack of published information about current doses of antipsychotic drugs actually being prescribed in everyday practise. This paper reports a study of the doses of antipsychotic drugs prescribed in an Australian psychiatric hospital Schizophrenia Unit.

Method Schizophrenia Unit, Hillcrest Hospital, Adelaide, South Australia, and The Queen Elizabeth Hospital, Woodville, South Australia, and The University of Adelaide, Adelaide, South Australia Chenie A. Galletly MB ChB, DPM, FRANZCP, Senior Visiting Psychiatrist and Clinical Lecturer

Patients The Schizophrenia Unit at Hillcrest Hospital, Adelaide, South Australia, has 24 acute and 34 subacute beds, serving a catchment population of ap-

CHERRIE A. GALLETLY

Data analysis Table I . Doses ojantipsychotic drugs in a schi:ophrenia inpatient unit

Data was grouped to show the percentage of patients prescribed more than 600 mg/day of chlorpromazine (or equivalent), and more than 1500 mg/day of chlorpromazine (or equivalent). Students t-test was used to compare the doses of low and high potency drugs, and to compare the total daily doses received by patients prescribed oral drugs only, and those receiving depot drugs.

- - - -

Acute ward

Sub-acute ward

Total

(n=31)

(n=38)

(n=69)

Daily dose (in mg chlorpromazine) 1500

58% 26% 16%

34%

45% 29% 26%

Average daily dose (mg chlorpromazine)

a37

1345

1126

34% 32%

Results Fifty five percent of patients were prescribed daily d o s e s e q u i v a l e n t t o m o r e than 600 mg of chlorpromazine. I

Low potency drugs proximately 700,000 people. The majority of patients have schizophrenia, but patients with other non-affective psychoses may also be admitted. Medication is prescribed by one of the four consultant psychiatrists, or by trainee psychiatrists under consultant supervision. Ward rounds held weekly in the acute ward and fortnightly in the sub-acute ward provide a formal review of each patient’s current treatment. All inpatients on 26/4/89 and 19/10/89 prescribed antipsychotic drugs were included in the study. Fourteen patients who were in hospital on both occasions were excluded from the second sample. There were 41 patients in the first sample (17 acute and 24 sub-acute) and 28 in the second sample (14 acute and 14 subacute).

Procedure Each patient’s daily dose of antipsychotic drugs was converted to the equivalent dose of chlorpromazine [8]. Using these conversion formulae, 2 mg of oral haloperidol, fluphenazine or pimozide, or 5 mg of thiothixene or trifluoperazine, are equivalent to 100 mg of chlorpromazine. A patient receiving 20 mg/day of haloperidol would therefore be receiving the equivalent of 1,000 mg/day of chlorpromazine. This study used the formula provided by the manufacturers (Squibb) for fluphenazine decanoate, which converts 25 mg/2 weeks to 293 mg/day of chlorpromazine. Variable schedule (prn) medication was excluded.

Seven percent of patients were prescribed low potency drugs only, and their average daily dose was equivalent to 410 mg of chlorpromazine. Patients prescribed high potency drugs only, or a combination of low and high potency drugs, had an average daily dose equivalent to 1370 mg chlorpromazine. This difference was significant ( t = 4.69, df = 67, p=50.0005).

Depot drugs Sixty one percent of patients were prescribed depot drugs. The majority (eighty percent) of patients prescribed depot drugs were also prescribed additional oral drugs. The average daily dose (including the oral drugs) of patients prescribed depot medication was equivalent to 1285 mg chlorpromazine, whilst patients prescribed oral medication only received an average daily dose equivalent to 893 mg chlorpromazine (t = 1.52, df = 67, p

Antipsychotic drug doses in a schizophrenia inpatient unit.

Dose-effect studies have found that 600 mg/day of chlorpromazine (or its equivalent) is generally sufficient to treat acute psychosis. This paper repo...
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