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“Drugs don't work if people don't take them.”1


“Why would someone who has gone to the trouble and expense of seeking out a physician, of undertaking arduous or uncomfortable tests and other diagnostic procedures, and of purchasing drugs and devices on the advice of the physician, then fail to follow the recommendations?”2


At the end of the chapter, the reader will be able to:


  1. Describe the optimal definition of suboptimal medication utilization

  2. Compare and contrast compliance, adherence, concordance, and persistence

  3. Compare and contrast initial compliance, partial compliance, compliance, and hypercompliance

  4. Discuss the advantages and disadvantages associated with the different methods of measuring medication utilization

  5. Describe the essential elements for calculating adherence and persistence from administrative claims data

  6. Calculate adherence/persistence from information contained in administrative claims data.

  7. Recognize challenges to using administrative claims data to measure adherence/persistence

  8. Recognize the elements that define a quality adherence and persistence study using administrative claims data


The effectiveness of a therapy depends on only two elements. First, the prescriber, with or without consultation with another health care provider (e.g., a pharmacist), must select a therapy that is appropriate in all aspects.3 In other words, assuming a correct diagnosis, the therapy must be the right drug, by the right route, in the right dose, at the right time, for the right duration, for the right patient.4 The second consideration is the extent to which the patient consumes the medications as recommended.3(p950) In terms of patient care, the detection of suboptimal medication utilization is a prerequisite for adequate treatment.5 Although the importance of proper diagnosis, medication selection, and treatment efficacy are not being debated, patient utilization of medication is the sole focus of this chapter.


Patients commonly fail to take their medications as directed, leading to additional diagnostics and treatments, unnecessary hospitalizations, avoidable nursing home admissions, and even death; estimates of the direct and indirect costs associated with suboptimal medication utilization exceed US$100 billion a year.6 Many nursing home admissions are due to no cause other than the patient's inability to manage his/her medications.7 When one considers the cost differences associated with patients living independently versus long-term care, the cost savings are tremendous. It is estimated that just over 5%8 of hospital admissions and between 1% and 3%912 of emergency department visits can be attributed to a patient's suboptimal medication utilization. Patients who exhibit better medication utilization (80%–100%) are significantly less likely to be hospitalized for disease-related reasons or for any other reason, compared with patients who exhibited suboptimal medication utilization.13 It is a well-regarded fact that patients who consume their medications in a manner consistent with expectations experience positive health outcomes and decreased mortality.14 However, in spite of increased knowledge and increased responsibility for their own care, patients still fail to follow the recommendations given by their health care providers about medication use....

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