RISPERIDONE - A PHARMACOECONOMIC REVIEW OF ITS USE IN SCHIZOPHRENIA

The availability of new atypical antipsychotics, such as risperidone, that have higher acquisition costs than conventional treatments has pr ompted pharmaco-economic evaluation of their costs and benefits. Rispe ridone is reported to have superior efficacy to haloperidol and simila r efficacy to other atypical antipsychotics. At dosages less than or e qual to 8 mg/day, risperidone is generally associated with a lower ris k of extrapyramidal symptoms than conventional antipsychotics and may have a more favourable effect on cognitive function and quality of lif e. Overall treatment costs during the first year of risperidone treatm ent were lower than in the previous year in a number of studies in pat ients with schizophrenia, reflecting a reduction in hospitalisation, a lthough costs slightly increased after risperidone initiation in 2 stu dies. Total treatment costs were not significantly different with risp eridone or conventional antipsychotics in a large, pro spective natura listic study. The use of risperidone in preference to conventional ant ipsychotics in patients with chronic schizophrenia has been supported by several modelled studies, including a cost-effectiveness analysis t hat compared risperidone and haloperidol in chronic schizophrenia and a cost-utility study that compared the drug with oral haloperidol, dep ot haloperidol decanoate and depot fluphenazine decanoate for 1 year's treatment of an initially hospitalised chronic schizophrenic patient with moderate symptoms, In another study, the cost-utility ratio for r isperidone versus haloperidol was 24 250 Canadian dollars per quality- adjusted life year (year of costing not stated), but only drug costs w ere considered. Risperidone had favourable cost-benefit ratios relativ e to conventional antipsychotic treatment in a study that investigated a scenario in which all patients hospitalised with newly diagnosed sc hizophrenia received conventional antipsychotic therapy for 6 months, and then those who did not respond received a 6-month trial of risperi done or clozapine. The results of 2 limited decision-analytical models did not favour risperidone, One study compared risperidone with oral haloperidol or depot haloperidol decanoate for the outpatient treatmen t of a schizophrenic patient with a history of relapse and rehospitali sation. The other compared risperidone, olanzapine and oral haloperido l for the treatment of schizophrenia. Conclusions: Despite its high ac quisition cost, risperidone does not increase, may even reduce, overal l treatment costs of schizophrenia by reducing hospitalisation compare d with standard treatment regimens. While further pharmacoeconomic eva luation of risperidone as a first-line agent is required, pharmacoecon omic data overall support its use in patients with chronic schizophren ia. Schizophrenia is a psychotic disorder that affects approximately 0 .5 to 1% of the population worldwide. It is expensive to treat because the age of onset is relatively young (late teens to mid-30s), the dis ease is often chronic and highly disabling and there is no cure. Hospi talisation is the greatest contributor to the direct costs of schizoph renia, whereas drug expenditure generally accounts for only about 1 to 6% of costs in developed countries. Indirect costs arising from loss of productivity can be greater than direct costs. Other costs include those related to social welfare administration and criminal justice, t he time spent by unpaid caregivers and the intangible costs associated with suffering. Although the exact cost of schizophrenia is difficult to determine, it has been calculated to account for 1.6 to 2.5% of to tal healthcare expenditure in various developed countries. Risperidone is effective against both the negative and positive symptoms of schiz ophrenia. About 50 to 75% of risperidone-treated patients were clinica lly improved (greater than or equal to 20% improvement in the Positive and Negative Syndrome Scale score) in short term comparative trials. The optimally effective dosage for patients with chronic schizophrenia is 4 to 6 mg/day; patients with first-episode schizophrenia appear to respond to lower dosages. Risperidone (4 to 8 mg/day or flexible dosa ges) has been reported to have superior clinical efficacy to haloperid ol. In short term comparative trials, the efficacy of risperidone was not significantly different from that of zuclopenthixol, amisulpride, clozapine and olanzapine and was superior to perphenazine on some meas ures. Risperidone may be more efficacious against negative symptoms (e .g. apathy, flattened affect, social or emotional withdrawal and pover ty of speech) than conventional antipsychotics. The drug can be effica cious in patients who are resistant to conventional antipsychotics. So me aspects of the cognitive impairment associated with schizophrenia a re improved by risperidone, and it has a more favourable effect on cog nitive functioning than conventional antipsychotics such as haloperido l and fluphenazine. Risperidone is generally well tolerated. At dosage s less than or equal to 8 mg/day, risperidone is not associated with a significantly greater incidence or severity of extrapyramidal symptom s (EPS) than placebo. At higher dosages, the risk of EPS is greater. I mportantly, risperidone less than or equal to 8 mg/day is associated w ith a lower risk of EPS than haloperidol. The incidence of EPS with ri speridone is similar to that with perphenazine and amisulpride, and si milar to or greater than that with clozapine. Patients treated with ri speridone are less likely to require concomitant antiparkinsonian medi cations than those receiving haloperidol or zuclopenthixol. Other adve rse events that have been reported during risperidone treatment includ e insomnia, anxiety, headache, orthostatic hypotension, dizziness, tac hycardia, bodyweight gain, somnolence/sedation, sexual dysfunction, na usea/vomiting and hyperprolactinaemia. However, the relationship of ma ny of these events to the drug has not been established. Unlike clozap ine, risperidone is not associated with significant haematological tox icity and has a low convulsant potential. The tolerability of risperid one is generally similar to or better than that of haloperidol. Risper idone appears to improve quality of life. Scores on the Global Assessm ent of Functioning or Quality of Life scale improved after the initiat ion of risperidone in 2 noncomparative studies involving a total of ap proximate to 1,500 evaluable patients. Quality of Life scale