**2. Medical adherence taxonomy**

"Drugs don't work in patients who don't take them" is the often-cited statement of Surgeon General of the United States C. Everett Koop (1985). Non-adherence is the major problem for pharmacotherapy in ambulatory patients. It is more prevalent than would be expected. It is highly associated with increased morbidity and mortality, and is an aspect that until recently was neglected. Despite its importance and all the efforts that have been made to understand it, non-adherence is still misunderstood. This behavior, in addition to the direct effects on the patient, since it compromises the preservation and the quality of her/his life, also has economic consequences. Therefore, in recent years, therapeutic adherence has been extensively studied from pharmacological, behavioral, economical perspectives [17]. Despite all the studies, the lack of uniformity in the methods of analysis and the absence of a universal taxonomy/ terminology are a major obstacle when making/analyzing systematic reviews, as it makes it difficult to draw conclusions.

*Compliance, adherence, concordance* and *persistence* are the four widely used terms that have been used interchangeably. *Adherence* and *compliance*, the mostly used terms have different connotations in the patient's attitude regarding medication. *Compliance* comes from the Latin word *complire*, meaning to fulfil a promise/to complete an action, implying that the patient has a passive role on the process. *Adherence* derives from the Latin word *adhaerere,* which means remain constant, keep close, having the patient agreed with the prescription [15, 18, 19]. Of the other two terms, *Concordance* implies that the patient and the professional healthcare came to an agreement about the treatment that the patient should follow, acknowledging that they may have different points of view, while *persistence* relates to the time interval between the first and the last dose of medicine [19–21].

Given this heterogeneity, it was necessary to obtain a consensus on the terminology and taxonomy in the field of non-adherence. The ABC project (Ascertaining Barriers to Compliance) was created under the seventh Framework Program, and the main objective was to provide consensus taxonomy and terminology in non-adherence medication and to provide concise and adequate definitions that could serve the needs of both clinical research and medical practice [22].

The ABC taxonomy relies on these three elements, making a clear distinction between procedures that describe actions through routines that have been established (m*edication adherence* and *management of adherence*) and the sciences that study those procedures (*adherence-related* 

**Figure 2.** The ABC taxonomy of medication adherence describing its three key elements and demonstrating how patients

Adherence to Medication in Older Adults as a Way to Improve Health Outcomes and Reduce…

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Of note, currently, the use of compliance has diminished, as this very term, for historical reasons, mostly, was perceived as the one that implies paternalistic relation between the doctor

Non-adherence to therapy is a public health problem in general, with a special focus on the elderly population. Non-adherence causes the patient outcome to be compromised, resulting in decreased effective disease control, increased risk of hospitalization and increased morbidity

and patients. Therefore, this term is not advised by the ABC taxonomy.

**3. Determinants of non-adherence**

*sciences*) [22].

can deviate.

and mortality [23].

*Medication adherence* is defined as an active, cooperative and voluntary participation of the patient in following recommendations from a healthcare provider. This is a multifactorial behavior that involves three critical steps (**Figure 2**).

*Management of adherence* has a main purpose to increase the benefit to the patient, and minimize the risk of harm, caused by the medication. It encompasses healthcare systems, providers, patients and their family/friend's networks, and serves to monitor and support patient's adherence to medication [22].

*Adherence-related sciences* include all the disciplines that study the causes and consequences of non-adherence, including medicine, nursing, sociology, biostatistics, pharmacy, behavioral science, pharmacometrics and health economics [19].

Adherence to Medication in Older Adults as a Way to Improve Health Outcomes and Reduce… http://dx.doi.org/10.5772/intechopen.72070 29

**Figure 2.** The ABC taxonomy of medication adherence describing its three key elements and demonstrating how patients can deviate.

The ABC taxonomy relies on these three elements, making a clear distinction between procedures that describe actions through routines that have been established (m*edication adherence* and *management of adherence*) and the sciences that study those procedures (*adherence-related sciences*) [22].

Of note, currently, the use of compliance has diminished, as this very term, for historical reasons, mostly, was perceived as the one that implies paternalistic relation between the doctor and patients. Therefore, this term is not advised by the ABC taxonomy.
