Electronic pillboxes (MEMS) to assess the relationship between medication adherence and blood pressure control in primary care

Abstract

Objective. To investigate the relationship between blood pressure and medication adherence using electronic pillboxes (MEMS). Setting. Five general practices in Bristol, UK. Subjects. A total of 239 individuals with a clinical diagnosis of hypertension and being prescribed at least one blood pressure-lowering medication. Participants were asked to use the electronic pillbox as their drug bottle for at least one month. Main outcome measures. "Timing adherence" (correct inter-dose intervals) as measured through MEMS and systolic (SBP) and diastolic (DBP) office blood pressure. Results. Mean (±SD) timing adherence was 88% (±17),>80% in 175 (73%), and less than 50% in 11 (5%) participants. Adherence was monitored for a mean of 33 (±6) days. Mean (±SD) SBP was 147.9±19.1 mmHg and DBP 82.3±10.1 mmHg. There was no evidence to suggest that timing adherence was associated with SBP or DBP (overall correlation coefficients -0.01 and -0.02 respectively). According to current guidelines, about one in four of all participants had controlled SBP (only 6% of diabetic patients). DBP was under control in 66% of the individuals. Conclusions. No relationship between adherence and blood pressure in patients with hypertension recruited from primary care was found. Average timing adherence measured by electronic monitors was high (88%) and blood pressure was controlled in a minority of patients. Our findings suggest that in terms of poor blood pressure control pharmacological non-response to or insufficient intensity of blood pressure-lowering medication might be more important than poor adherence to antihypertensive drug therapy. © 2007 Taylor & Francis.