RISPERIDONE VERSUS HALOPERIDOL - II - COST-EFFECTIVENESS

Australia and Canada are currently the only Western nations with gover nment guidelines for analyzing the cost-effectiveness of drugs. We use d guidelines issued by the Australian Pharmaceutical Benefits Advisory Committee to construct a model for comparing the cost-effectiveness o f risperidone and haloperidol over a 2-year period in patients with ch ronic schizophrenia. Use of clozapine was also included in the analysi s as an alternative treatment given to patients who proved unresponsiv e to therapy with haloperidol or risperidone. Results are expressed in Australian dollars. Cost-effectiveness was determined by using decisi on-analytic modeling to compare clinical outcomes and costs, The analy tic model contained a decision tree for each of the compared agents th at tracked the distribution of patients between treatment outcome path ways (ie, scenarios), Distributions were based on probabilities derive d from our meta-analysis results reported elsewhere and from other sou rces. Each scenario had an associated monetary cost that included all significant direct costs (ie, hospital costs; outpatient costs; and th e cost of drugs, the services of health care professionals, and govern ment-subsidize hostel accommodation). The cost for a given outcome was the sum of costs for all scenarios leading to that outcome. Cost-effe ctiveness was expressed as the total cost per favorable outcome. The d efinition of a favorable outcome was one in which the patient was in a response phase at the end of the 2-year period. The probability of a patient experiencing a favorable outcome at the end of 2 years was 78. 9% for risperidone versus 58.9% for haloperidol. The total cost of tre atment for 2 years was $15,549.00 for risperidone versus $18,332.00 fo r haloperidol. The expected cost per favorable outcome was $19,709.00 for risperidone and $31,104.00 for haloperidol. Risperidone was more c ost-effective than haloperidol and therefore was ''dominant'' in pharm acoeconomic terms because it produced a higher proportion of favorable outcomes at lower cost. Sensitivity analysis showed that the differen ce in clinical response rate was a key determinant of cost-effectivene ss.