Promoting adherence to antibiotics: A test of implementation intentions

Abstract

Objective

This prospective study tested whether implementation intentions increased adherence to short-term antibiotics in a patient sample. Implementation intentions specify exactly when and where an individual will undertake an activity. They may help people achieve health behaviours, such as taking medicines.

Methods

A total of 220 patients with an antibiotics prescription were randomly assigned to four groups (control, Theory of Planned Behaviour (TPB) questionnaire, TPB questionnaire + formed own implementation intention for taking the medicine, TPB questionnaire + researcher formed implementation intention). Participants were telephoned at the end of the course to record adherence. Two hundred and seven participants completed the study.

Results

At follow-up, adherence was high (75.8% reported no tablets left). Analysis revealed no significant difference in adherence between groups.

Conclusion

High adherence to antibiotics was achieved, but not improved by implementation intentions.

Practice implications

Providing information and telephone follow-up may have been the unintended effective intervention in this study.

Introduction

Antimicrobial agents (described hereafter as antibiotics) have enabled huge advances in medicine [1]. However, their use selects for resistant bacteria and once selected, these bacteria can spread or transfer their resistant genes to other bacteria, resulting in the reduced future efficacy of antibiotics [1]. There are now resistant strains of nearly all bacteria with some bacteria becoming resistant to many medicines [2]. Indeed, tackling the problem of antimicrobial resistance is considered to be an international public health challenge [1], [2], [3], [4], [5].

An important contributing factor to the increasing resistance to antibiotics is where patients do not take the course of antibiotics as directed, i.e. missing doses or not completing the course. Antibiotics prescribed for acute conditions typically have a 5 to 10 day course, to be taken two to four times daily. Because of the action of these medicines it is important that patients do not miss doses, as this may jeopardise the efficacy of treatment. This is in contrast to many other medications, particularly those taken for preventive reasons that are often taken just once daily and whose effect is less influenced by non-adherence.

Adherence to short-term courses of antibiotics in primary care ranges from approximately 30 to 99% based on a variety of self-report and objective adherence measures [6], [7], [8], [9], [10]. Given this broad range, it is difficult to gauge the true extent of the problem of non-adherence. Although we do know that better adherence to these therapies is associated with less frequent doses and shorter lengths of treatment [6], [11]. Importantly, non-adherence can lead to failure to eradicate the organism and subsequent promotion of resistance. This is in addition to the negative effects on the individual's health and public health.

Current strategies to improve adherence to short-term courses of prescribed medicines are not particularly effective and are under-researched. In a systematic review of interventions to help patients follow prescriptions for medications [12] only three interventions for short-term treatments were identified and only one achieved significant improvements in adherence. Furthermore, these interventions were atheoretical [12]. In designing interventions to tackle the problem of non-adherence, it is important to distinguish between intentional and non-intentional non-adherence [13], [14]. Barber [13] adapted Reason's Theory of Human Error [15] to classify intentional non-adherence as violations that are deliberate (not getting a prescription dispensed) and mistakes made despite having the right intention (not getting emergency supply). For actions of this nature, interventions need to be aimed at changing an individual's beliefs, fostering personal control and removing perceived obstacles [16]. Assuming that intention is the immediate precursor of behaviour [17], the aim of remediation is to strengthen the intention to adhere. In contrast, non-intentional non-adherence includes slips that are caused by lack of attention (taking the wrong tablet) and lapses that result from memory failure (forgetting a dose). This type of non-adherence can be reduced through interventions that enhance awareness and aid memory.

Implementation intentions [18], [19], [20] are a useful framework for tackling non-intentional non-adherence. These are specific plans that outline exactly when, where and how performance of a behaviour is to be achieved and are presented as ‘I intend to do X at time Y in place Z’. It is proposed that implementation intentions work by passing control of the behaviour from the individual to the environment [18], [19]. By specifying when and where the behaviour will be performed, it becomes linked to the environmental cue, which leads to the automatic elicitation of action when this cue is encountered. In other words, the responsibility for remembering to perform the behaviour is taken away from the individual [21].

Increasing evidence suggests that implementation intentions are effective in moving people towards achieving behavioural goals. Three meta-analyses of data from multiple studies have tested implementation intentions in achieving goals and performing behaviours [21], [22], [23] and have reported medium effect sizes of 0.63, 0.54 and 0.70. In terms of health behaviours, a recent systematic review [24] found that implementation intentions (rather than implementation intentions plus a motivational intervention) significantly increased performance of health behaviours compared to controls in 8 of the 14 studies reviewed. This effect was evident across a range of health behaviours, including cervical cancer screening [25], [26], breast [27] and testicular self-examination [28], exercise [29] and reducing binge drinking [30].

Some support for implementation intentions in promoting daily taking of medicines has been demonstrated using Vitamin C tablets [31], [32]. Sheeran and Orbell [32] in two studies found that students who supplemented goal intentions (“I intend to take these Vitamin C tablets”) with implementation intentions (“I will take a Vitamin C tablet at time Y in place X”) missed taking fewer tablets (P < 0.05) in 3 weeks than students who formed a goal intention only. There was no significant difference between the two groups after only 10 days.

To date, there has been no test of implementation intentions to increase adherence to prescribed medicines in a patient population. The scale and implications of non-adherence to medicines is an area of focus worldwide [5] and notably in the UK [33], [34]. Implementation intentions may be a simple, cost- and time-effective strategy for pharmacists and other practitioners to employ. From a public health perspective, students may not be representative of the groups of people that need to take prescribed medicines, thus research with patient populations is urgently required.

Gollwitzer [19] argues that the stronger the individual's commitment to the implementation intention, the stronger the effect on behaviour. However, little is known about what factors affect commitment to implementation intentions. For example, is it important for the individual to form the implementation intention oneself rather than be told by a pharmacist about a suitable time or place for medicine-taking? This is a particularly important consideration given the current emphasis on partnership in medicine-taking [35].

The study reported here tested whether implementation intentions could increase adherence to short-term antibiotic regimens in a patient sample. It also investigated whether forming an implementation intention oneself would result in greater adherence than being given instructions about when and where the antibiotics should be taken by a health professional.