How often do pharmacology textbooks address medication adherence?

Introduction

Pharmacology depends on many factors that affect pharmacokinetics, including absorption, excretion and metabolism of drugs. Adherence to treatment, whether patients take or apply the drug, is an equally fundamental factor that affects both efficacy and safety of medications. From topical to oral to injectable medications, from diseases as diverse as psoriasis to diabetes, adherence to medications is poor (1–5). Better medication adherence improves patient outcomes and has the potential to reduce healthcare costs by preventing unnecessary hospitalizations (6). Poor adherence is a particular challenge in the field of dermatology, given the preponderance of chronic diseases and messy, inconvenient topical medications that are the mainstay of therapy in dermatological diseases (7,8).

Anecdotally, it has been our impression that the topic of adherence is not adequately addressed in medical school curricula. The Liaison Committee for Medical Education (LCME) has set forth curricular standards required for medical schools to attain (and maintain) accreditation, which are contained within their publication, “Functions and Structure of a Medical School” (9). Although, the LCME requires that medical school curricula address many other important aspects of being a good physician, such as communication skills and cultural competence, there is no mention of medication adherence. The purpose of this study was to examine the coverage of adherence in pharmacology texts as compared to two other important pharmacology concepts, drug excretion and bioavailability.

Methods

A search of the Wake Forest School of Medicine Carpenter Library online textbook inventory was performed to identify electronic pharmacology texts. Three texts were selected on the basis of availability and ability to electronically search: Basic and Clinical Pharmacology (10), McGraw-Hill 2014; Goodman & Gilmans: The Pharmacologic Basis of Therapeutics (11), McGraw-Hill 2011 and A Pharmacology Primer (12), Elsevier 2009. The first edition of Goodman & Gilmans was published in the early 1940s, and it is considered by many to be one of the most widely used texts for pharmacology, and even is considered by some to be “the bible of pharmacology” (13). Basic and Clinical Pharmacology is also quite popular, with a search of Amazon.com revealing that it is the #5 top seller in the “Books > Medical Books > Pharmacology > Clinical” subcategory as of February 15, 2015. It is the top selling textbook in that category (14). A Pharmacology Primer, a non-clinical pharmacology textbook, provides an example of a textbook that provides more succinct coverage of pharmacology.

For each textbook, every chapter was searched electronically for the words “adherence”, “adherent”, “adhere”, “adhered”, “compliance”, “compliant”, “comply”, “excretion”, “excreted”, “excrete”, “excretory”, “bioavailability” and “bioavailable”. We excluded from the count each instance in which adherence or compliance referred to something other than adherence to treatment, for example, eosinophil adherence. We compared the number phrases relating to adherence and compliance (combined) to phrases relating to excretion and to bioavailability. Any repetitive phrases, such as those mentioning that both adherence and compliance can be used interchangeably, were excluded. We calculated and expressed the frequency with which medication adherence and compliance were mentioned as a fraction of both excretion and bioavailability for each text. The frequencies of adherence and compliance mentions in the book chapters to excretion or bioavailability mentions were compared using Chi-squared test.

Results

In Basic and Clinical Pharmacology, adherence was mentioned in fewer chapters than excretion (p < 0.0001) and bioavailability (p = 0.055). Adherence-related terms were mentioned once for every five times excretion appeared and once for every two times bioavailability appeared (Figure 1). Goodman & Gilmans: The Pharmacologic Basis of Therapeutics also addressed adherence in fewer chapters than excretion (p < 0.0001) and bioavailability (p = 0.003). Adherence was mentioned once for every 11 and 3 times excretion and bioavailability were mentioned, respectively. In A Pharmacology Primer, adherence was also mentioned in fewer chapters than excretion (p = 0.28) and bioavailability (p = 0.14). Adherence was mentioned roughly once for every two times both excretion and bioavailability was mentioned.

Figure 1. Total number of occurrences of adherence, excretion and bioavailability in each textbook.

We also compared the percentage of chapters in which each textbook mentioned adherence, excretion and bioavailability (Table 1). The two clinical pharmacology textbooks were similar in the proportion of chapters which mentioned adherence. In Basic and Clinical Pharmacology, 41% of chapters mentioned adherence versus 91% for excretion and 58% for bioavailability (Figure 2). In Goodman & Gilmans: The Pharmacologic Basis of Therapeutics, 42% of chapters mentioned adherence versus 85% for excretion and 67% for bioavailability. In A Pharmacology Primer, 7% of chapters mentioned adherence versus 25% for excretion and 33% for bioavailability.

Figure 2. Percentage of chapters in which adherence, excretion and bioavailability were mentioned in each textbook.

Table 1. How often adherence, excretion and bioavailability are mentioned in each textbook.

	Adherence	Excretion	Bioavailability
Basic and Clinical Pharmacology (66 chapters)
Total # times mentioned	81	435	172
# chapters mentioned	27	60	38
% chapters mentioned	41	91	58
Goodman & Gilmans: The Pharmacologic Basis of Therapeutics (67 chapters)
Total # times mentioned	77	818	263
# chapters mentioned	28	57	45
% chapters mentioned	42	85	67
A Pharmacology Primer (14 chapters)
Total # times mentioned	12	29	32
# chapters mentioned	1	3	4
% chapters mentioned	7	25	33

Discussion

Adherence to medication is an important factor in treatment efficacy. Pharmacology education often focuses on medication bioavailability and excretion but is relatively weaker in coverage of one of the most important factors that determines drug levels and efficacy in clinical practice, how well patients take the medication. Both clinical pharmacology books mentioned adherence and compliance with similar frequency, however Goodman & Gilmans: The Pharmacologic Basis of Therapeutics mentioned excretion and bioavailability much more frequently. Basic and Clinical Pharmacology seemed to have more of a focus on adherence to medication, and even contains a subchapter focusing on compliance, and mentioning various reasons for non-adherence to medication. A Pharmacology Primer mentioned adherence less than excretion and bioavailability, however, the results were not statistically significant.

Concepts such as bioavailability and excretion are critical factors in pharmacology because they affect blood levels and drug effects. Adherence is another critical determinant of blood levels and drug effects. Furthermore, adherence to topical medication is even worse than systemic drugs, and can even vary based on the type of vehicle used (7).

Medical schools are becoming more and more cognizant of integrating clinical medicine in the basic science portions of medical education (15). Inadequate attention to adherence may not prepare future dermatologists (and other physicians) to be sufficiently cognizant of the importance adherence to medication has in their patients’ response to therapy.

The evolving healthcare climate is putting increased emphasis on outcomes for the basis of reimbursement, with an estimated 30% of Medicare reimbursements to be based on outcomes measures in 2016 (16). In many dermatological diseases, treatment failure can be attributed to poor adherence rather than poor response to the medication. Focusing on providing education on adherence early on in medical education would help to ensure that future dermatologists would keep in mind the importance of poor adherence in their patients’ outcomes.

This study has several limitations. First, it is limited in the breadth of textbooks examined. Furthermore, while it gives a sense of how often adherence is mentioned, this study does not delve into the depth at which it is covered when it is mentioned. Since many students use other resources besides textbooks, by examining these books we are only getting a partial understanding of the extent that is covered in medical education.

Patients are human, not test tubes, and patient adherence to medication is, therefore, fundamental to clinical pharmacology. Variation among patients in their adherence to treatment may explain more of the variability in response to treatment than variation in absorption, metabolism, excretion or receptor binding. The role of patient adherence to treatment should be emphasized in medical education, however additional research may be needed to determine how adherence can be best integrated into preclinical education.

Declaration of interest

The Center for Dermatology Research is supported by an unrestricted educational grant from Galderma Laboratories, L.P. Dr. Feldman is a consultant and speaker for Galderma, Stiefel/GlaxoSmithKline, Abbott Labs, Warner Chilcott, Janssen, Amgen, Photomedex, Genentech, BiogenIdec and Bristol Myers Squibb. Dr. Feldman has received grants from Galderma, Astellas, Abbott Labs, Warner Chilcott, Janssen, Amgen, Photomedex, Genentech, BiogenIdec, Coria/Valeant, Pharmaderm, Ortho Pharmaceuticals, Aventis Pharmaceuticals, Roche Dermatology, 3M, Bristol Myers Squibb, Stiefel/GlaxoSmithKline, Novartis, Medicis, Leo, HanAll Pharmaceuticals, Celgene, Basilea and Anacor and has received stock options from Photomedex. Dr. Barnes, Mr. Farhangian and Mrs. Huang have no conflicts to disclose.

No ethical approval was required for this study.

This article was not funded by any grants.