The economic and clinical impacts of prescribing antidepressant, antconvulsant and antipsychotic medications off-label for patients with schizophrenia, bipolar disorders, depression and anxiety
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The objective of this study was to 1) estimate the prevalence of using antidepressant, anticonvulsant and antipsychotic medications off-label, 2) explore factors associated with these off-label uses and 3) determine the effects of using these medications off-label on total health expenditures, inpatient hospitalizations and emergency room (ER) visits in Medicaid enrollees with schizophrenia, bipolar disorders, depression, or anxiety. Georgia Medicaid data (1999-2001) were obtained from the Georgia Department of Community Health. In the outcomes analysis, four disease-specific cohorts were constructed for patients with schizophrenia, bipolar disorders, depression and anxiety disorders. Within each cohort, the treatment group was formed of subjects who received off-label antidepressant, anticonvulsant or antipsychotic medications at the beginning of a 12 months observation period, while the comparison group consisted of subjects who did not receive these off-label medications for the entire observation period. Differences in annual outcomes were estimated between propensity score matched off-label and on-label users. Rosenbaum bounds sensitivity analysis was performed to test the robustness of the outcome estimates against hidden bias. 46,976 (75.42%) antidepressant recipients, 38,497 (80.12%) anticonvulsant recipients and 21,252 (63.62%) antipsychotic recipients received at least one of these medications off-label in 2001. Recipients older than 64 were four to six times more likely to receive an off-label prescription relative to those younger than 40. The off-label users experienced significantly higher per capita annual prescription expenditures across the cohorts (net difference: schizophrenia cohort $892.88; bipolar cohort $555.51; depression cohort: $783.87; anxiety cohort: $640.72). Besides prescription costs, the off-label users in the depression cohort also had higher outpatient, inpatient, long-term care and mental health related expenditures, which in total, resulted in a $2,209.36 average cost difference between the off-label and the on-label groups. The off-label users in the schizophrenia cohort incurred significantly lower hospital utilizations and expenditures. In conclusion, the off-label use of antidepressant, anticonvulsant and antipsychotic medications is highly prevalent. Using these medications off-label is associated with significantly increased prescription expenditures across all mental disorders under investigation. For other outcome measures including medical expenditures, ER and hospital utilizations, the influences of off-label drug use are heterogeneous in different mental disorders.