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Am J Manag Care. 2005 Nov;11(11):670-4.

The effect of switching on compliance and persistence: the case of statin treatment.

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  • 1Department of Pharmaceutical Economics and Policy, School of Pharmacy; University of Southern California, 1540 East Alcazar Street, CHP 140, Los Angeles, CA 90033, USA.



To determine the effect of switching drugs on the compliance and persistence of new statin users.


Retrospective database analysis of pharmacy claims provided by a large pharmacy benefit manager. The study sample consisted of 38 866 new statin users 18 to 65 years old beginning treatment with atorvastatin calcium, fluvastatin sodium, lovastatin, pravastatin sodium, or simvastatin.


Compliance was measured by the "medication possession ratio," and persistence was measured by the time to discontinuation. Switching rates were derived from the proportions of patients filling a prescription other than the initial statin.


Patients who switched statins were less compliant by 18.9% (odds ratio, 0.81; P < .001), as defined by the probability of having a medication possession ratio of 0.8 or higher, and were less persistent by 20.9% to 48.3% (P < .001) depending on the gap length used to define discontinuation.


Switching statins substantially reduces the likelihood that patients will be compliant and remain on treatment long enough to obtain the full benefit of statin treatment. To ensure better compliance, special care should be given to patients who change drugs.

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