Patient adherence to prescribed medication instructions for dyspepsia: The DIAMOND-study

Background: Insight into patient adherence is needed to enable an effect evaluation of medication for dyspepsia. Objectives: Adherence was explored by investigating two adherence outcome measures (completeness and intake fidelity) using data from the DIAMOND-study. Methods: The DIAMOND-study is a pragmatic RCT comparing a 'step-up' with a 'step-down' treatment strategy. In step 1 participants (n = 653) were instructed to use five pills/day for maximally 30 days: an antacid 4dd plus a placebo 1dd ('step-up') or a proton pump inhibitor 1dd plus a placebo 4dd ('step-down'). If the complaints persisted, step 2 was started (H-2-receptor antagonist 2dd), and subsequently step 3 (five pills/day, placebo and verum vice versa from step 1). Completeness was assessed by pill counts, intake fidelity by patient questionnaires measuring the degree to which patients adhered to specific instructions concerning timing, frequency, dose and way of intake. Results: In step 1, patients used on average 3.9 pills/day (78% of the prescribed doses), in step 2, 1.7 pills/day (85%) and in step 3, 3.6 pills/day (72%). For the four times daily pills, half of the patients used less than 80% of the prescribed pills per day. This was one third of the patients for the twice daily pills and one quarter for the once daily pills. There were no completeness differences between active or placebo medication and no differences between the study arms. As regards intake fidelity, 70% of the patients made one or more errors in the medication intake. Conclusion: There is room for improvement in adherence rates for dyspepsia medication.