Center for the Assessment of Pharmaceutical Practices Papers
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Item An alternative approach to measuring treatment persistence with antipsychotic agents among patients with schizophrenia in the Veterans Health Administration(Dove Medical Press, 2007) Ren, Xinhua S.; Qian, Shirley; Kazis, Lewis E.Prior studies have demonstrated the importance of treatment persistence with anti-psychotic agents in sustaining control of schizophrenic symptoms. However, the conventional approach in measuring treatment persistence tended to use only the first prescription episode even though some patients received multiple prescriptions (or multiple treatment episodes) of the same medication within one year following the initiation of the index drug. In this study, we used data from the Veterans Health Administration in the United States to assess the extent to which patients received multiple prescriptions. The study found that about a quarter of the patients had two or more treatment episodes and that levels of treatment persistence tended to vary across treatment episodes. Based on these results, we offered an alternative approach in which we calculated treatment persistence with typical and atypical antipsychotic agents separately for patients with one, two, or three treatment episodes. Considering that patients with different number of treatment episodes might differ in disease profiles, this treatment episode-specific approach offered a fair comparison of the levels of treatment persistence across patients with different number of treatment episodes. Future research needs to extend the analyses beyond two antipsychotic classes to individual antipsychotic agents. A more comprehensive assessment using appropriate analytic methods should help physicians make prescription choices that will ultimately improve the care of patients with schizophrenia.Item Measurement of treatment adherence with antipsychotic agents in patients with schizophrenia(Dove Medical Press, 2009-10-12) Ren, Xinhua S.; Herz, Lawrence; Qian, Shirley; Smith, Eric; Kazis, Lewis E.The importance of medication adherence in sustaining control of schizophrenic symptoms has generated a great deal of interest in comparing levels of treatment adherence with different antipsychotic agents. However, the bulk of the research has yielded results that are often inconsistent. In this prospective, observational study, we assessed the measurement properties of 3 commonly used, pharmacy-based measures of treatment adherence with antipsychotic agents in schizophrenia using data from the Veterans Health Administration during 2000 to 2005. Patients were selected if they were on antipsychotics and diagnosed with schizophrenia (N = 18,425). A gap of ≥30 days (with no filled index medication) was used to define discontinuation of treatment as well as medication "episodes," or the number of times a patient returned to the same index agent after discontinuation of treatment within a 1-year period. The study found that the 3 existing measures differed in their approaches in measuring treatment adherence, suggesting that studies using these different measures would generate different levels of treatment adherence across antipsychotic agents. Considering the measurement problems associated with each existing approach, we offered a new, medication episode-specific approach, which would provide a fairer comparison of the levels of treatment adherence across different antipsychotic agents.Item Simvastatin is associated with a reduced incidence of dementia and Parkinson's disease(BioMed Central, 2007-7-19) Wolozin, Benjamin; Wang, Stanley W.; Li, Nien-Chen; Lee, Austin; Lee, Todd A.; Kazis, Lewis E.BACKGROUND: Statins are a class of medications that reduce cholesterol by inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A reductase. Whether statins can benefit patients with dementia remains unclear because of conflicting results. We hypothesized that some of the confusion in the literature might arise from differences in efficacy of different statins. We used a large database to compare the action of several different statins to investigate whether some statins might be differentially associated with a reduction in the incidence of dementia and Parkinson's disease. METHODS: We analyzed data from the decision support system of the US Veterans Affairs database, which contains diagnostic, medication and demographic information on 4.5 million subjects. The association of lovastatin, simvastatin and atorvastatin with dementia was examined with Cox proportional hazard models for subjects taking statins compared with subjects taking cardiovascular medications other than statins, after adjusting for covariates associated with dementia or Parkinson's disease. RESULTS: We observed that simvastatin is associated with a significant reduction in the incidence of dementia in subjects ≥65 years, using any of three models. The first model incorporated adjustment for age, the second model included adjusted for three known risk factors for dementia, hypertension, cardiovascular disease or diabetes, and the third model incorporated adjustment for the Charlson index, which is an index that provides a broad assessment of chronic disease. Data were obtained for over 700000 subjects taking simvastatin and over 50000 subjects taking atorvastatin who were aged >64 years. Using model 3, the hazard ratio for incident dementia for simvastatin and atorvastatin are 0.46 (CI 0.44–0.48, p < 0.0001) and 0.91 (CI 0.80–1.02, p = 0.11), respectively. Lovastatin was not associated with a reduction in the incidence of dementia. Simvastatin also exhibited a reduced hazard ratio for newly acquired Parkinson's disease (HR 0.51, CI 0.4–0.55, p < 0.0001). CONCLUSION: Simvastatin is associated with a strong reduction in the incidence of dementia and Parkinson's disease, whereas atorvastatin is associated with a modest reduction in incident dementia and Parkinson's disease, which shows only a trend towards significance.