Hidden high-dose antipsychotic prescribing: effects of p.r.n. doses

The study investigated the reasons influence medical staffs' choice of a specific drug over another given the same clinical situation, by use of a questionnaire-based survey. The study population Responses In the factors: personal experience, scientific evidence, Influence from colleagues, economic consideration, Influence by drug representatives, ward or unit policy and other in choice of prescription, were the main outcome measures.

Hidden high-dose antipsychotic prescribing: effects of p.r.n. doses John Milton, John Lawton, Mark Smith and Ann Buckley

Aims and method The Royal College of Psychiatrists'
Consensus Statement on 'The use of high-dose antipsychotic medication' suggests only fully qualified psychiatrists (MRCPsych) should recommend the prescribing of high-dose antipsychotic treatment. We observed changes in anti-psychotic prescribing in two surveys of psychiatric In-patients conducted eight and 32 months after publication of the Consensus Statement. Results Overall mean chlorpromazine equivalent doses of antipsychotic drugs reduced between the surveys. When p.r.n. (as required) prescribing (usually done by junior doctors) is included, mean potential doses and numbers of patients who might receive 'high-doses' increases substantially, although the reduction between surveys in total mean dose and proportion of patients on high-dose antipsychotic medication is preserved, and the actual use of p.r.n. medication was low (4-5% of p.r.n. prescriptions).
Clinical implications We recommend the development of local guidelines for junior staff concerning antipsychotic drug prescribing, regular monitoring of p.r.n. medication by consultants, and pharmacists' involvement in reviews of patients prescribed highdose antipsychotic medication.
both mean antipsychotic doses and the pro portion of patients prescribed high-dose antipsychotic medication after the Consensus Statement (Cornwall et al. 1996: Pinner & Edgar. 1996. Further studies have highlighted the influence of as required (p.r.n.) prescriptions on the overall dose of antipsychotic medication. Although New ton et ai (1997) found only 2% of in-patients were prescribed high-dose antipsychotic medication, all as a direct result of p.r.n. prescribing, this contrasts with their calculation of 42.4% of patients prescribed high-dose antipsychotic medication in another study (Krasucki & McFarlane, 1996), also when p.r.n. prescriptions were included.
The aims of our surveys were to observe changes in high-dose antipsychotic medication prescribing post-Consensus Statement and to examine the influence of (p.r.n.) medication, usually prescribed by junior psychiatrists, on the proportion of patients receiving high-dose antipsychotic medication.

The study
The surveys took place within Nottingham Healthcare's hospital in-patient and dispersed rehabilitation sites, which have replaced the larger mental hospital-based services. The pre scription cards of all adult acute, rehabilitation and open forensic ward psychiatric in-patients were examined on two occasions, eight and 32 months after publication of the Consensus Statement. Data collected included daily dose of regular oral and depot medication and maximum daily dose of p.r.n. medication prescribed (but not necessarily given). Demographic information, including diagnosis and whether compulsorily detained, was obtained separately. High-dose antipsychotic medication prescribing was de fined as a total daily dose (oral and depot) >1000mg chlorpromazine equivalents (calcu lated from BNF (Number 33, March 1997) and Bazire (1997), see Table 1). All consultants were given written information about their prescribing following the 1994 survey and the results presented to the local postgraduate meeting.

Findings
One hundred and sixty-one of 200 (81%) patients in 1994, and 193 of 230 (84%) in 1996, were receiving regular antipsychotics. There were no significant differences between the two years for gender (62 v. 63% male), mean age (37 v. 39 years) or proportion of patients detained under the Mental Health Act 1983 (36 v. 34%). Table 2 shows a comparison of the mean regular chlorpromazine equivalents for each year and Table 3 lists the number of patients prescribed high-dose antipsychotic medication, excluding and including p.r.n. medication for each year. Actual dispensing of p.r.n. medication occurred on seven occasions (4% of patients) in the 1994 survey and 10 occasions (5% of patients) in the 1996 survey.

Comment
Overall mean chlorpromazine equivalent doses have reduced since 1994 for all psychiatric inpatients in Nottingham. There may be several reasons for this. First, this may reflect an increased awareness of the potential hazards of prescribing antipsychotics at high dose, both from the Consensus Statement and from feed back following our 1994 survey. Second, pre scribing of atypical antipsychotic drugs (clozapine and risperidone) showed a small increase between the surveys (5.5% in 1994 to 7.8% in 1996) although it was not clear from our data if the group taking atypical antipsychotic drugs in the 1996 survey had previously been prescribed high-dose antipsychotic medication treatment. Third, the data also reveal consider able variation in prescribing practices between different consultant teams present in both surveys and between prescribers present in only one of the surveys which may have influenced the total mean dose. The effect of this variable on dose of antipsychotic prescribed is currently subject to further analysis.
Although also reduced, a notable number (20 v. 25% in 1994) of psychiatric in-patients were still regularly receiving antipsychotic doses in excess of 1000mg chlorpromazine equivalents per day in 1996. This figure is higher than recent in-patient surveys from other areas (Torkington et al, 1994;Warner et al, 1995) and may have two explanations. Our survey included a number of rehabilitation and open-ward forensic patients (approximately 45% in each year) who often receive higher doses than general psychiatric patients. Because of our largely communitybased service, it might be speculated that those patients actually requiring hospital admission are more severely ill, reflected by higher rates of compulsory admission (Singh et al, 1998) and have greater levels of behavioural disturbance prompting prescribing of higher doses of medi cation but not necessarily benefiting from them.
When p.r.n. prescribing is also taken into account, this results in a statistically significant increase, both in the mean dose in chlorpromazine equivalents per day and in the number of patients who fall into the 'high-dose' category for each year. This is usually as a result of prescribing by junior (often non-MRCPsych) psychiatrists and contrary to the Consensus Statement guidelines. Although the actual dis pensing of p.r.n. medication occurs infrequently (4-5% of p.r.n. prescriptions) and suggests that the issue of injudicious prescribing is in practice less clinically relevant than initially expected, we believe that it still reflects a hidden potential for the unwitting prescription of high doses.
It is clear from the Consensus Statement that there is little evidence from controlled clinical trials for the superior effectiveness of high-dose antipsychotic medication prescribing, even for behavioural control. Therefore the addition of p.r.n. doses to already high-dose prescribing would appear to rarely have any clinical justifi cation. We would recommend regular surveys and audit of antipsychotic prescribing and the devel opment of local guidelines for junior staff on good prescribing practice. These guidelines should address, in particular, the area of cautious p.r.n. prescribing by juniors and monitoring by consultants. We would also encourage identifica tion of those patients on high-dose antipsychotic medication and suggest frequent medication reviews involving pharmacists. BAZIRE. S. (1997)