The concept of patient adherence to medications is simple and clearly exemplified by Koop’s law: “Drugs don’t work in patients who don’t take them”. A scientific background is not needed to understand this concept. There are, however, multiple, drug-specific consequences of non-adherence that are not self-evident, but nevertheless contribute in major ways to undesirable outcomes and costs.

Non-adherence has long been considered to be a patient-issue, but today it is also recognized as a systems problem, wherein not only the patient is involved but also the healthcare system and the quality of caregivers’ help. As such, patient adherence stands at the intersection of many different disciplines: medicine, nursing, pharmacy, pharmacometrics, health economics, biostatistics, drug regulation, and pharmaceutical R&D and marketing. Therefore the understanding of patient nonadherence and its many consequences challenges one’s understanding of prescription drugs, their actions -- both beneficial and potentially harmful – and the associated economic impact.

Meeting this multi-disciplinary challenge begins with a widely-accepted, robust taxonomy for adherence. Recently published (1), this taxonomy defines three elements of drug treatment: initiation, implementation, and discontinuation. These elements are dynamic, for they change over time and thus require richly-sampled measurements to quantify adequately their roles in the management of drug treatment. The causes of non-adherence, whether intentional or not, are multiple, and sometimes difficult to identify. Their consequences vary, depending on the disease and its severity, concomitant diseases and their respective severities, and the totality of medications used in the patient’s care. There is a huge literature on various aspects of these matters, but its value is severely compromised by unreliable data arising from poor methods of measurement – a problem substantially overcome by the advent of electronic methods to compile patients’ dosing histories during ambulatory care.

Thus the need for reliable data on patients’ dosing histories to:1) inform patients and caregivers when dosing errors have occurred and how best to minimize adverse consequences thereof; 2) reinforce each patient’s understanding of the benefits and hazards of the medications they have been prescribed; 3) provide timely information on what to do when doses have been missed; 4) reinforce information on the benefits of continued persistence with drugs prescribed for long-term use.

Recent research has revealed many gaps in the information needed to support effective management of medication. Closing those gaps is now a priority issue in ambulatory care, as reliable methods are now available to implement measurement-guided medication management. It requires joint involvement of physicians, nurses, pharmacists, and specialists from the disciplines enumerated above in paragraph 2. The results of such integrative analysis stand to improve ambulatory care and its outcomes and economics, as perceived within the multiple perspectives of the aforementioned disciplines.

Reference:
1. 1. Vrijens, B, deGeest S, Hughes D, et al. A new taxonomy for describing and defining adherence to medications. Brit J Clin Pharmacol 2012;73:691-705. ta

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