Association between antipsychotic combination therapy and treatment adherence among individuals with bipolar disorder.

BACKGROUND: This study investigated the effect on antipsychotic treatment adherence of combining quetiapine or risperidone with lithium, anticonvulsants, and/or antidepressants among bipolar individuals with predominantly manic/mixed or depressive symptoms. METHODS: Treatment episodes with quetiapine or risperidone were identified from individuals with medical claims for bipolar/manic disorder. Multiple regression analysis was used to evaluate the impact of antipsychotic combinations on treatment adherence, as measured by intensity (medication possession ratio [MPR]) and treatment duration. RESULTS: Among mixed/manic individuals, combination therapies were associated with lower antipsychotic MPRs than monotherapy (P< .05), with MPR decreasing with number of medications. Quetiapine showed a similar pattern among depressed individuals, whereas risperidone showed a weaker association. For both subgroups, antipsychotic combinations with anticonvulsants were associated with lower MPRs than combinations with lithium. For manic/mixed individuals, combining quetiapine with an anticonvulsant and lithium was associated with shorter treatment durations than quetiapine alone (P

The association between treatment adherence and antipsychotic dose among individuals with bipolar disorder.

Claims data were examined to evaluate the association between antipsychotic dose and treatment adherence among individuals with predominantly manic/mixed or depressed symptoms of bipolar disorder. Two measures of treatment adherence were used, intensity (medication possession ratio) and treatment duration (uncensored treatment episodes). Effects of higher antipsychotic doses on adherence were evaluated using multiple regression analysis. Dose effects on adherence intensity in subsequent (3-month) treatment stages were examined over 15 months. Antipsychotic treatment episodes (13 921) were analyzed. For manic/mixed individuals, risperidone, olanzapine, and typical antipsychotics showed reduced adherence intensity with higher doses in all treatment stages (P<0.05). Among depressed individuals, higher doses of olanzapine and typical antipsychotics were associated with reduced adherence intensity in all stages, with most associations reaching significance (P<0.05). Higher doses of quetiapine and risperidone were associated with increased adherence intensity in months 4-6 (P<0.05), but risperidone showed reduced intensity in months 7-9 (P<0.001). For all risperidone-treated or quetiapine-treated individuals, higher doses were associated with longer treatment durations (P<0.05). Higher doses of olanzapine and typical antipsychotics (and in manic/mixed individuals, risperidone as well) seem to adversely impact adherence intensity. Among depressed individuals, higher doses of quetiapine and risperidone are initially associated with increased adherence intensity.

Antipsychotic treatment adherence and associated mental health care use among individuals with bipolar disorder.

BACKGROUND: Up to 48% of patients with bipolar disorder are either nonadherent or partially adherent to antipsychotic drug treatment. Medication adherence may differ by bipolar disorder subtype. OBJECTIVE: This study evaluated the association between antipsychotic treatment adherence and mental health care use among individuals with bipolar disorder with predominantly manic/mixed symptoms or predominantly depressive symptoms. METHODS: Individuals with bipolar or manic disorder who had at least 1 medical claim with International Classification of Diseases, Ninth Revision, Clinical Modification codes 296.4-296.8 (bipolar disorder) or 296.0 or 296.1 (manic disorder) were identified from medical and pharmacy claims in the PharMetrics database for the period from January 1999 through December 2004. Adherence was measured by intensity (medication possession ratio [MPR]) and treatment duration. The association between adherence and health care use during and after antipsychotic treatment was evaluated using multiple regression analysis. The traditional P < 0.05 threshold was used for statistical significance; however, results that approached significance at P < 0.10 were also noted. RESULTS: Claims data were examined for 13,941 antipsychotic treatment episodes occurring in 12,952 individuals with bipolar or manic disorder. Of these, 6153 treatment episodes occurred in 5711 individuals with predominantly manic/mixed symptoms, and 2617 occurred in 2381 individuals with predominantly depressive symptoms. The remaining 5171 treatment episodes occurred in 4860 individuals with unspecified bipolar disorder and were not included in the analysis. In individuals with manic/mixed symptoms, a higher MPR was associated with reduced total and outpatient mental health expenditures over subsequent stages of treatment (reduction in total expenditure per 1-point increment in MPR: $123-$439; P < 0.001). In individuals with predominantly depressive symptoms, the association between MPR and subsequent mental health expenditure reached statistical significance only in months 10-12, the 3rd of the 4 treatment segments examined (total mental health expenditure: -$714 [P < 0.001]; outpatient mental health expenditure: -$468 [P < 0.001]). A higher MPR was also associated with a lower likelihood of acute mental health care (inpatient hospitalization or an emergency department visit) in subsequent months in individuals with manic/mixed symptoms or depressive symptoms (odds ratio = 0.545 [95% CI, 0.30- 1.00] and 0.395 [95% CI, 0.14-1.12], respectively; both NS at the P < 0.05 threshold), and was not associated with mental health inpatient days. In both subgroups, a longer duration of treatment was associated with lower total and outpatient mental health expenditures during the 4 months after the termination of treatment (both, P < 0.01). CONCLUSIONS: In these individuals with bipolar or manic disorder, improved adherence to antipsychotic treatment was associated with lower subsequent total and outpatient mental health care expenditures. This association was less pronounced in individuals with predominantly depressive symptoms than in those with predominantly manic/mixed symptoms.

Hospitalization risks in the treatment of bipolar disorder: comparison of antipsychotic medications.

OBJECTIVES: This study compared the relative risk for hospitalization of patients with bipolar and manic disorders receiving atypical and typical antipsychotics. METHODS: This retrospective study was based on administrative claims data extracted from the PharMetrics database during 1999 through 2003. Comparisons were made among atypical antipsychotics (risperidone, olanzapine, quetiapine or ziprasidone), as well as between each of these versus a combined group of the leading typical antipsychotics. Relative risk for hospitalization was estimated with Cox proportional regression, which adjusted for differences in patient characteristics. RESULTS: Risperidone and olanzapine demonstrated higher risks for hospitalization than quetiapine [hazard ratio (HR) 1.19, p < 0.05 for both], translating into higher annual mental health inpatient charges of $260 per patient. Risperidone and olanzapine also showed higher estimated risks than ziprasidone, which approached the p < 0.05 threshold. Differences between each of the atypicals and the combined typicals were not significant. Patients with putative rapid cycling had a threefold greater risk for hospitalization than other patients with bipolar disorder. In these patients, comparisons among atypical antipsychotics showed that risperidone had a significantly higher hospitalization risk than olanzapine (HR 3.31, p < 0.05), resulting in higher annual mental health inpatient charges of $4,930 per patient. CONCLUSIONS: In the treatment of bipolar and manic disorders, risperidone and olanzapine were associated with a higher risk for hospitalization than quetiapine, and possibly ziprasidone. In the treatment of putative rapid cyclers, olanzapine was associated with a lower risk for hospitalization than risperidone.

Treatment adherence among patients with schizophrenia treated with atypical and typical antipsychotics.

This study evaluated treatment adherence among patients with schizophrenia receiving atypical and typical antipsychotics. Claims data for 7017 treatment episodes of commercially insured patients with schizophrenia (ICD-9-CM) receiving antipsychotics, covering the period from January 1999 through August 2003, were assessed. Overall adherence was evaluated by adherence intensity (medication possession ratio) and treatment duration (length of treatment episode). Pair-wise comparisons of the individual atypicals and a combined group of leading typical antipsychotics were undertaken using multiple regression, adjusting for differing patient characteristics. Each atypical antipsychotic demonstrated a significantly higher adherence intensity than the combined typicals, while quetiapine demonstrated a significantly greater adherence intensity than risperidone and olanzapine. None of the atypicals showed treatment durations significantly different from the typicals. While the small improvements in adherence intensity among atypical agents do not appear to be clinically important, they may reflect an underlying, stronger tendency to use filled prescriptions.

Hospitalization risks in the treatment of schizophrenia: comparison of antipsychotic medications.

This study used administrative claims data to compare the relative risks for hospitalization among commercially insured patients with schizophrenia receiving atypical and typical antipsychotic drugs. Cox proportional hazard regression estimates, adjusted for differences in patient characteristics, suggested that among patients treated with the 4 atypical antipsychotic drugs, only olanzapine had a significantly higher risk for hospitalization than the typical antipsychotic drugs (hazard ratio [HR], 1.81; 95% confidence interval [CI], 1.20-2.75). In addition, risk for hospitalization with olanzapine was significantly higher than that for risperidone (HR, 1.34; 95% CI, 1.03-1.74) and numerically higher than that for quetiapine (HR, 1.40; 95% CI, 0.94-2.07). Overall, olanzapine was associated with a higher risk for hospitalization than the typical antipsychotic drugs and among the atypical antipsychotic drugs, risperidone and, potentially, quetiapine.

Treatment adherence among patients with bipolar or manic disorder taking atypical and typical antipsychotics.

OBJECTIVE: This retrospective claims-based study evaluated treatment adherence among patients with bipolar or manic disorder treated with atypical and typical antipsychotics. METHOD: Claims data for 18,158 antipsychotic treatment episodes in 15,224 commercially insured patients with bipolar or manic disorder (ICD-9-CM criteria), from January 1999 through August 2003, were evaluated. Overall adherence was measured by adherence intensity (medication possession ratio) and treatment duration (length of treatment episodes). Treatment-related factors that may affect medication adherence were also investigated. Pairwise comparisons of the individual atypicals and a combined group of leading typical antipsychotics were undertaken using multiple regression analysis adjusting for differing patient characteristics. RESULTS: Adherence intensity with quetiapine was 3% greater than with the typicals combined (p=.002) and was greater than with risperidone or olanzapine by 4% (p<.001) and 2% (p=.001), respectively. Olanzapine (2%, p<.001) and ziprasidone (3%, p=.001) showed significantly greater adherence intensity than risperidone. Risperidone (p=.002), olanzapine (p=.055), and the typicals (p=.021) demonstrated negative associations between dose and adherence intensity, while quetiapine showed a nonsignificant trend for a positive association (p=.074). Quetiapine and risperidone had significantly longer treatment durations than the typicals combined (1.05 and 1.00 months, respectively, p<.001) and longer treatment durations than olanzapine (0.75 and 0.79 months, respectively, p<.001) or ziprasidone (0.78 months, p=.002 and 0.69 months, p=.003, respectively). Shorter treatment durations were associated with switching to other antipsychotics or remaining on or switching to other psychotropics (e.g., traditional mood stabilizers) only. All of the atypicals except ziprasidone were associated with a significantly lower likelihood of switching compared with the typicals (p<.05). CONCLUSIONS: The claims-based findings of this study suggest that, for bipolar or manic disorder, quetiapine therapy may be associated with better treatment adherence than typical or some atypical antipsychotics. Estimated differences, however, were relatively small, particularly for adherence intensity.

The influence of study design on the results of pharmacoepidemiologic studies of diabetes risk with antipsychotic therapy.

BACKGROUND: Retrospective large patient database studies have reported conflicting findings regarding diabetes risks associated with antipsychotics. This study compared two study designs to assess antipsychotic-related diabetes risk. METHODS: Claims data were analyzed for over 60,000 patients with psychosis, both treated and untreated with antipsychotics, between January 1999 and April 2002. Diabetes odds ratios for patients treated with antipsychotics versus untreated patients were estimated. All patients and patients stratified by low, medium, and high antipsychotic dose were analyzed. Logistic regression controlled for age, sex, type of psychosis, length of observation/treatment, preexisting excess weight, and use of other drugs. RESULTS: Under a less rigorous study design, diabetes risk was statistically significant with all antipsychotics versus no treatment. Under a more rigorous design, relative odds for quetiapine and risperidone declined and became statistically nonsignificant, whereas those for olanzapine and conventional antipsychotics increased and remained significant. By dose, only quetiapine showed a lack of statistical significance at all dose levels. CONCLUSIONS: In database studies estimated risks of antipsychotic-related diabetes are affected by study design. With a more rigorous design, the risk associated with quetiapine and risperidone was not significantly different from that in untreated patients. These findings may explain inconsistent findings in pharmacoepidemiologic database studies.

Assessment of antipsychotic-related risk of diabetes mellitus in a Medicaid psychosis population: sensitivity to study design.

PURPOSE: The effect of study design on findings regarding diabetes risk associated with antipsychotics was studied. METHODS: This study was a retrospective analysis of data from more than 100,000 Medicaid patients. Diabetes odds ratios (ORs) for patients treated with clozapine, olanzapine, quetiapine, risperidone, ziprasidone, or conventional antipsychotics versus untreated patients were estimated with and without the following design enhancements: screening for preexisting diabetes, selecting for antipsychotic monotherapy, and identifying diabetes with prescription claims only. Logistic regression controlled for patient sex, race and ethnicity, type of psychosis, length of observation and treatment, antipsychotic dosage, pre-existing excess weight or dyslipidemia, and use of other drugs with potential diabetogenic effects. RESULTS: Under the weakest study design (none of the above enhancements), all antipsychotics were associated with significantly higher odds of diabetes relative to no treatment (p < 0.05). Estimated ORs were as follows: clozapine, 1.468; olanzapine, 1.108; quetiapine, 1.270; ziprasidone, 1.226; risperidone, 1.232; and conventional antipsychotics, 1.159. Under the strongest design (all of the above enhancements), ORs relative to no treatment were significant for clozapine (1.484) and olanzapine (1.149) and nonsignificant for quetiapine (0.998), risperidone (1.124), ziprasidone (0.717), and conventional antipsychotics (1.025). The data also strongly suggest selection bias by clinicians (i.e., selecting antipsychotics based on preexisting diabetes or risk factors for diabetes), disfavoring risperidone and favoring olanzapine. Although the evidence is weaker, quetiapine may also have been affected by unfavorable selection bias. CONCLUSION: In large database studies, estimated risks of diabetes among patients treated with antipsychotics appeared to be influenced by study design. When a more rigorous design was used, only clozapine and olanzapine were associated with diabetes risk significantly greater than that in untreated patients.

Relationship between initial quetiapine dose and effectiveness as reflected in subsequent mental health service use among patients with schizophrenia or bipolar disorder.

OBJECTIVE: To investigate the association between initial quetiapine dose and effectiveness as gauged by subsequent use of mental health services. METHODS: Using a health plan database, we identified patients with bipolar disorder or schizophrenia treated with quetiapine monotherapy for at least four consecutive months. The stability of each patient before and after quetiapine treatment was measured by use of mental health services other than antipsychotic drug, measured primarily by charges reported on claims. Regression models controlling for patient differences measured associations between initial quetiapine dose and subsequent mental health service use. RESULTS: Commercially insured patients with schizophrenia (n = 581) or bipolar disorder (n = 2421) received quetiapine monotherapy at mean (SD) initial daily doses of 237 (198) mg and 147 (171) mg, respectively. Both groups showed negative associations between initial daily dose and subsequent mental health charges. Among patients with schizophrenia, mental health charges decreased by US 1.28 dollars for each additional milligram of quetiapine (P = 0.1097). Among patients with bipolar disorder, there was a significant decrease of US 1.31 dollars per additional milligram of quetiapine (P = 0.0484). For schizophrenia, hospitalizations were reduced by 0.4% for each additional milligram of quetiapine (P = 0.0189). For bipolar disorder, the association between quetiapine dose and outpatient charges was negative and trended toward significance (P = 0.074), showing a US 0.54 dollars reduction in these charges for each additional milligram of quetiapine; the association with hospitalization was not significant. CONCLUSIONS: In patients with schizophrenia or bipolar disorder, higher initial doses of quetiapine may be more effective in stabilizing patients as reflected in lower subsequent mental health service use.

Effects of patients with bipolar, schizophrenic, and major depressive disorders on the mental and other healthcare expenses of family members.

Family members who live with patients with serious mental disorders incur increased healthcare expenses. A retrospective study measured these increased expenses using administrative data from a large Blue Cross Blue Shield health plan in the USA. Mental and other healthcare expenses of family members of patients with bipolar disorder, schizophrenia, or major depression were compared to those of control family members. Ordinary least squares and logistic regression were used to estimate differences. In comparison with control (families of two or more members without these psychiatric disorders), mental and other healthcare expenses per family member per month were increased for subject family members as follows: bipolar disorder, $8.85 (213%; P<0.0001) and $10.65 (7.4%; P<0.0001); schizophrenia, $4.03 (81%; P<0.0001) and $5.96 (4.2%; P<0.005); and major depression $8.24 (219%; P<0.0001) and $9.46 (6.5%; P<0.0001). Among other factors, older family members had a greater likelihood of using mental healthcare and higher levels of other healthcare; males were less likely than females to use mental healthcare but had higher levels of other healthcare, and managed forms of coverage were associated with higher levels of both mental and other healthcare. We conclude that living with a person with serious mental illness significantly increases healthcare expenses of family members, especially mental healthcare. Family members of patients with bipolar disorder and major depression experienced larger increases in expenses than family members of patents with schizophrenia, despite the fact that patients with schizophrenia were more seriously ill as reflected in the much higher mental healthcare expenses of these patients.

Comparison of mental health resources used by patients with bipolar disorder treated with risperidone, olanzapine, or quetiapine.

OBJECTIVE: The atypical antipsychotics, risperidone, olanzapine, and quetiapine, have been approved by the U.S. Food and Drug Administration for treatment of mania associated with bipolar disorder. Information on the relative mental health resource use of these therapies is helpful to pharmacy managers since differences in efficacy and safety may translate into differences in mental health care utilization. We compared charges for other mental health services associated with risperidone, olanzapine, and quetiapine treatment of patients with bipolar disorder to assess whether there were significant differences between these therapies. A secondary analysis involved dose-equivalent adjustment of the average allowed charge of the 3 atypical antipsychotics. METHODS: This was a retrospective study based on administrative data for 46 U.S. commercial health plans represented in a commercial database covering the period January 1998 through April 2002. The 6,625 patients included in the study had at least 2 contiguous pharmacy claims for a study antipsychotic, had received no other antipsychotics concurrently, and had not switched from an alternative antipsychotic in the preceding 90 days. Provider-submitted (billed) charges were selected in preference to paid amounts as being more accurate indicators of relative differences in the use of mental health resources. Mental health care charges were measured per patient per month (PPPM) and included charges for the study antipsychotics and charges for the other mental health care services (inpatient, physician and other ambulatory, and other psychotropic medications). Differences in other mental health care charges PPPM among the 3 therapies were assessed with multivariate regression, adjusting for differing patient characteristics. Differences in antipsychotic drug charges PPPM were assessed after adjustment to reflect an equivalent average daily dose. RESULTS: Regression estimates adjusted for patient differences did not show statistically significant differences in other mental health care charges PPPM among the 3 antipsychotic drug therapies. Other mental health charges associated with quetiapine were estimated to be 14 US dollars, or 3% lower than those associated with risperidone, but this difference was not statistically significant (P = 0.069). The PPPM charges for quetiapine versus olanzapine and olanzapine versus risperidone were also not different (P = 0.231 and P = 0.39, respectively). After adjusting for differences in average daily dose, risperidone and quetiapine had antipsychotic drug charges that were 84 US dollars and 76 US dollars PPPM lower than those of olanzapine (P < 0.01); the difference between the adjusted drug charges PPPM for risperidone and quetiapine was not significant. CONCLUSION: Total charges for mental health services other than the study drug were not different for risperidone, olanzapine, and quetiapine in patients treated for bipolar disorder. However, based on prescription charges, olanzapine appears to be considerably more costly at an equivalent daily dose than either risperidone or quetiapine.

Antipsychotic-induced type 2 diabetes: evidence from a large health plan database.

Case evidence suggests that some of the atypical antipsychotics may induce type 2 diabetes. The objective of this study was to evaluate the association of antipsychotic treatment with type 2 diabetes in a large health plan database. Claims data for patients with psychosis within a health plan of nearly 2 million members were analyzed using logistic regression. Frequencies of newly treated type 2 diabetes in patients untreated with antipsychotics and among patients treated with quetiapine, risperidone, olanzapine, and conventional antipsychotics were compared. Based on exposure measured in months of antipsychotic treatment, quetiapine and risperidone patients had estimated odds of receiving treatment for type 2 diabetes that were lower than those of patients untreated with antipsychotics (not statistically significant); patients treated with conventional antipsychotics had estimated odds that were virtually equivalent to those of patients untreated with antipsychotics; olanzapine alone had odds that were significantly greater than those of patients untreated with antipsychotics (P = 0.0247). Odds ratios based on 8 months of screening for pre-existing type 2 diabetes and assuming 12 months of antipsychotic treatment were: risperidone = 0.660 (95% CI 0.311-1.408); olanzapine = 1.426 (95% CI 1.046-1.955); quetiapine = 0.976 (95% CI 0.422-2.271); and conventional antipsychotics = 1.049 (95% CI 0.688-1.613). Case reports, prospective trials, and other retrospective studies have increasingly implicated olanzapine and clozapine as causing or exacerbating type 2 diabetes. Few have implicated risperidone while evidence on quetiapine has been limited. This study supports earlier findings on risperidone versus olanzapine and builds evidence on quetiapine. Additional studies are needed to evaluate the association of antipsychotic treatment with type 2 diabetes.

Differential effects of antipsychotic agents on the risk of development of type 2 diabetes mellitus in patients with mood disorders.

BACKGROUND: Atypical antipsychotics are being used increasingly in the management of mood disorders. OBJECTIVE: The objective of this study was to investigate the association between exposure to antipsychotic therapy and newly reported type 2 diabetes mellitus in patients with mood disorders. METHODS: Claims data for the period January 1996 through December 1997 were analyzed for patients with mood disorders in 2 large US health plans. Logistic regression models were used to determine the odds of reporting diabetes in patients exposed to risperidone, olanzapine, or high- or low-potency conventional antipsychotics compared with untreated patients, taking into account duration of treatment and dosage. Some of the covariates used in the models were concurrent use of antipsychotics, use of other psychotropic drugs, age, sex, and length of observation. RESULTS: Based on the claims data, 849 patients were exposed to risperidone, 656 to olanzapine, 785 to high-potency conventional antipsychotics, and 302 to low-potency conventional antipsychotics; 2644 patients were untreated. The odds of newly reported type 2 diabetes in patients who received risperidone were not significantly different from those in untreated patients (12-month odds ratio [OR] = 1.024; 95% CI, 0.351-3.015). The odds in patients treated with high-potency conventional antipsychotics also did not differ significantly from those of untreated patients (12-month OR = 1.945; 95% CI, 0.794-4.786). Unlike patients who received risperidone or high-potency conventional antipsychotics, patients who received olanzapine (12-month OR = 4.289; 95% CI, 2.102-8.827) and low-potency conventional antipsychotics (12-month OR = 4.972; 95% CI, 1.967-12.612) had significantly higher odds for the development of type 2 diabetes compared with untreated patients. CONCLUSIONS: These findings suggest that some antipsychotics may increase the risk for the development of type 2 diabetes in patients with mood disorders and that the effect may vary by drug. In contrast to olanzapine and low-potency conventional antipsychotics, risperidone and high-potency conventional antipsychotics were not associated with an increased risk for development of type 2 diabetes in this patient population.

Differential effects of risperidone, olanzapine, clozapine, and conventional antipsychotics on type 2 diabetes: findings from a large health plan database.

BACKGROUND: Case series suggest that some antipsychotics may induce or exacerbate type 2 diabetes. This study measured the association of antipsychotic treatments with diabetes at a population level. METHOD: Claims data for psychosis patients (ICD-CM-9 290.xx-299.xx) within health plans encompassing 2.5 million individuals were analyzed. Patients reporting preexisting type 2 diabetes up to 8 months prior to observation were excluded. The frequency of newly reported type 2 diabetes in untreated patients and among patients treated with antipsychotics from 5 categories (risperidone, olanzapine, clozapine, and high-potency and low-potency conventionals) was compared. Logistic regression models compared the odds of diabetes based on exposure to each of the antipsychotic categories. RESULTS: Based on 12 months of exposure, the odds of type 2 diabetes for risperidone-treated patients (odds ratio = 0.88, 95% CI = 0.372 to 2.070) was not significantly different from that for untreated patients, whereas patients receiving other antipsychotics had a significantly greater risk of diabetes than untreated patients (p < .05): olanzapine, 3.10 (95% CI = 1.620 to 5.934); clozapine, 7.44 (95% CI = 0.603 to 34.751); high-potency conventionals, 2.13 (95% CI = 1.097 to 4.134); and low-potency conventionals, 3.46 (95% CI = 1.522 to 7.785). Older age and greater use of non-antipsychotic psychotropic medications also contributed to risk of type 2 diabetes. Olanzapine also showed significantly higher (p < .01) odds of diabetes associated with increasing dose. CONCLUSION: Consistent with previously published literature, these data suggest that olanzapine, clozapine, and some conventional antipsychotics appear to increase the risk of acquiring or exacerbating type 2 diabetes and that the effect may vary by drug. In contrast to these agents, risperidone was not associated with an increased risk of type 2 diabetes.

Methods for claims-based pharmacoeconomic studies in psychosis.

Pharmacoeconomic studies using claims data are frequently employed to compare the healthcare costs associated with competing drugs. Different methodological approaches with varying limitations for evaluating claims data are reviewed within the context of psychosis. Intent-to-treat paradigms and mirror-image designs have limitations that can bias comparisons of health resource use and can be addressed through the use of drug treatment episodes. Health resource use is better measured in financial rather than volume amounts, to account for service intensity. However, financial measures reported in claims records need to be carefully chosen. Between-group comparisons are frequently affected by selection bias, and within-group comparisons are often limited by period bias. While selection bias can be addressed by controlling for patient factors such as disease severity, and period bias by controlling for trend, devising appropriate control measures from the limited information in claims data can be challenging. Healthcare data are often skewed, which affects statistical testing. While skewed data are commonly handled through log transformation, this method has serious limitations, potentially distorting pharmacoeconomic comparisons. Determining the most appropriate methods for claims-based data involves careful evaluation of the alternate approaches to best achieve the goals of a pharmacoeconomic investigation.

Use of healthcare services by patients treated with risperidone versus conventional antipsychotic agents.

OBJECTIVE: To determine whether the use of risperidone in a US managed-care environment is associated with a reduction in the use of mental healthcare services. METHODS: Mental health service use and costs for patients with psychoses treated with risperidone versus those treated with conventional antipsychotic agents were compared by both between-group and within-group comparisons. The study controlled for differences between the groups. Only direct medical costs were considered. All costs were for the years 1994 to 1996. PERSPECTIVE: US managed care plan. RESULTS: Costs (excluding antipsychotic drug costs) per member per month (PMPM) were 180 US dollars lower with risperidone (p < 0.05); per member per year (PMPY) costs were 2160 US dollars lower. In patients who received both risperidone and conventional treatments, PMPM costs were 212 US dollars (2544 US dollars PMPY) lower during risperidone treatment. Total costs (including antipsychotic drug costs) were 624 US dollars PMPY lower with risperidone by between-group comparisons and 1008 US dollars PMPY lower by within-group comparisons. CONCLUSIONS: These results show that higher risperidone acquisition costs are offset by reductions in other mental healthcare costs, particularly inpatient hospitalisation costs. This indicates that risperidone may be a more economical choice than traditional antipsychotics for the treatment of psychoses.