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【社会人文】临床医师处方权的责难
Although there appears to be widespread support of evidence-based medicine as a basis for rational prescribing, the challenges to it are significant and often justified. A multitude of factors other than evidence drive clinical decision-making, including patient preferences and social circumstances, presence of disease-drug and drug-drug interactions, clinical experience, competing demands from more pressing clinical conditions, marketing and promotional activity, and system-level drug policies.
Introduction
Evidence-based medicine (EBM) can be defined as the integration of best research evidence with clinical expertise and patient values.[1] The recent transition from authority-based medicine to EBM has driven fundamental changes in clinical practice, health research, and medical education. This transition has generally been applauded, although its implementation has been difficult and sometimes harmful.[2] Major challenges facing evidence-based prescribing may be organized into 3 categories: (1) the availability of relevant evidence, (2) the time and ability to interpret evidence appropriately, and (3) the translation of knowledge into clinical practice. Using statin prescribing patterns as a case example, we discuss each of these 3 categories.
Several statins with similar safety profiles are currently available, providing clinicians with a variety of treatment options for reducing low-density lipoprotein cholesterol (LDL-C) levels. The case described here examines the impact of the introduction of new statins on clinician prescribing behavior among patients receiving long-term therapy with older members of the drug class.
We conducted a population-based cross-sectional time series analysis using administrative healthcare databases that cover more than 1.4 million residents of Ontario, Toronto, Canada, aged at least 66 years. These patients have universal access to prescription drug coverage, hospital care, diagnostics, laboratory tests, and physician services. This study was approved by the Ethics Review Board of Sunnybrook and Women's College Health Sciences Centre.
The linked databases included computerized pharmacy records of the Ontario Drug Benefit Program, which records prescription drugs dispensed to all Ontario residents 65 years of age and older and contains prescription-related information such as date of dispensing, drug strength, quantity dispensed, and intended duration of therapy. An overall error rate of less than 1% in this drug database has been reported.[3]
The study's timeframe was divided into 45 quarterly intervals from the first quarter in 1994 (1994Q1) to the first quarter in 2005 (2005Q1). At the beginning of each quarter, we identified long-term users of 2 relatively older statins—simvastatin and pravastatin. We defined long-term statin users as individuals who used the same statin for at least 3 consecutive 120-day intervals. Two relatively newer statins—atorvastatin and rosuvastatin—were included in the Ontario provincial formulary in August 1997 and September 2003, respectively. For both simvastatin and pravastatin, our main outcome measure was the percentage of long-term users who switched statin therapy as defined by the new dispensing of a statin other than the one used for 3 consecutive 120-day intervals. We also examined the most recent dose of the older statin prior to the switch to determine whether switched users were taking the maximum dose of simvastatin or pravastatin prior to switching. Time series analysis,[4] an approach for modeling autocorrelation in temporally sequenced data, was used to evaluate changes over time.
Availability of Relevant Evidence
Although there has been a considerable increase in clinical research activity recently, optimal evidence is often not available for many clinical decisions. Ideally, clinicians require well-designed, large-scale clinical studies that assess patients reflective of common clinical practice who are being treated with the drug of interest and all clinically relevant comparators, with sufficient follow-up to allow for the assessment of clinically meaningful patient outcomes.
In our case example, such trials existed for both pravastatin[5] and simvastatin[6] that demonstrated significant reductions in clinically meaningful outcomes such as myocardial infarction and death from coronary heart disease. These trials were published well before the introduction of atorvastatin and rosuvastatin. In contrast, a considerably smaller trial examining a surrogate endpoint, changes in levels of LDL-C, was published 7 months after the availability of atorvastatin on the public formulary in Ontario.[7] This trial suggested that atorvastatin was more potent than other statins in reducing LDL-C levels. Although LDL-C levels are correlated with atherogenesis, such a surrogate endpoint is not a replacement for more clinically meaningful outcomes, as evidenced by recent ezetimibe/simvastatin data suggesting possible cardiovascular harm despite greater LDL-C level reduction relative to simvastatin alone.[8] Indeed, recent evidence suggests that pravastatin, simvastatin, and atorvastatin may not differ significantly with respect to long-term clinical outcomes.[9] Similar data assessing surrogate endpoints in small trials accompanied the addition of rosuvastatin to the public formulary.
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作者:admin@医学,生命科学 2011-04-02 05:11
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