Modern anti-epileptic drugs (AEDs) aim not only to prevent seizures, but also to avoid unpleasant side-effects. However their success depends upon a person following a specific treatment plan. It has been shown that failure to comply with AED therapy (non-adherence) can result in increased seizure frequency, more ambulance call-outs and a greater number of hospital admissions. In addition, those whose AED intake is irregular appear to be at a greater risk of sudden death.

Unfortunately, evidence suggests that 30-50% of adults with epilepsy do not adhere to their AED schedules, and that non-adherence is the most common cause of treatment failure in the epilepsy population. Many do not admit an irregular AED intake to their neurologists, however, meaning that the extent of this problem is often underestimated.

In a recent study, Dr Markus Reuber and colleagues from the University of Sheffield examined whether a simple intervention could improve the AED adherence rates of people with epilepsy.

Recruitment to the study was undertaken by a team of five consultant neurologists, from the Royal Hallamshire Hospital in Sheffield. They enlisted a total of 81 people from their outpatient clinics between January and June 2007.

All participants fulfilled a list of criteria - for example they had all been clinically diagnosed with epilepsy, they were taking at least one AED and they were responsible for taking their own medication. It was also important that no one was already using an adherence intervention measure, because involvement in this research could have interfered with this.

Each of the 81 people was randomly allocated to either an intervention group or a control group. The neurologists, nurses and pharmacy staff were not aware who had been placed in each group.

In the first stage of the study, all participants were asked to complete a 14-page questionnaire of self-report measures; for example illness perception and estimated missed doses in the previous month. This was to ensure equivalence between the members of both groups and identify any factors that could limit the trialled intervention.

The intervention consisted of one worksheet, completed in addition to the 14-page questionnaire. It asked participants to identify everyday environmental 'prompts' for tablet taking, using a specific format known as an if-then plan - for example "If I am doing____ and it is___ O'clock, then I will take my tablet." This encouraged participants to think about exactly when they would take their medication each day and what they would be doing at that time.

This is known as 'intention implementation (II)', and the worksheet was thus referred to as an intention implementation intervention (III). Earlier studies showed that people tend to achieve a greater level of adherence using II, than with other conscious statements such as "I will take my medication on time every day." This is because II creates a direct association between the taking of the tablet and a specific activity performed each day, meaning that it is more likely to be remembered. Dr Reuber and his team used this evidence when choosing the style of their intervention.

Having completed their respective questionnaires, all participants collected a 1-month supply of their AED in a special electronic pill-monitoring bottle. Bottles such as this make a record of the number of times they are opened and when, and are a means of monitoring drug adherence. The bottle cap can be connected to a computer and the data can be viewed and printed.

At the end of the month, the participants received a letter, asking them to complete a follow-up questionnaire and return the pill-monitoring device.

When Dr Reuber and his team analysed the data from the electronic pill-monitoring devices, they looked at three outcome measures to gage adherence: percentage of doses taken, percentage of days on which the correct dose was taken and percentage of doses taken on schedule. If a bottle was opened within +/- 3 hours of the target time, the dose was recorded as having been taken on schedule.

Data analysis following the study showed some promising results:

Of the original 81 participants, 69 completed all stages of the study (37 in the intervention group, 32 in the control group). The intervention group demonstrated improved adherence across all of the outcomes measured:

The data also suggested that non-adherence was more likely to be a result of memory difficulties, than lack of desire to take the medication or carelessness. Interestingly, it was these people who had memory problems or actively reported missing doses who benefited most from the intervention.

The researchers acknowledge that their study has limitations and that further investigations need to be performed to ascertain the value of their II worksheet. For example the duration of their study (1 month) was relatively short; the intervention group was not monitored before they started the II (therefore there is no proof that the results weren't due to differences in illness perception rather than the intervention itself); neither seizure control, nor biological indicators of adherence (such as blood AED levels) were measured.

Nonetheless, they conclude that their II tool is a promising intervention for improving AED adherence. If further research supports this conclusion, III could potentially benefit both people with epilepsy and the NHS in the future.

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