Assessing Medication Adherence Simultaneously by Electronic Monitoring and Pill Count in Patients With Mild-to-Moderate Hypertension

Hein A. W. van Onzenoort, Willem J. Verberk, Alfons G. H. Kessels, Abraham A. Kroon, Cees Neef, Paul-Hugo M. van der Kuy, Peter W. de Leeuw*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


BACKGROUND Poor adherence to antihypertensive medication is one of the major problems in the treatment of hypertension. Electronic monitoring is currently considered to be the gold standard for assessing adherence, but it may trigger patients to open the pill bottle without taking medication or to take out more than prescribed. In adjunct to electronic monitoring, pill count could be a valuable tool for exploring adherence patterns, and their effects on blood pressure reduction. METHODS Among a total of 228 patients with mild-to-moderate hypertension, adherence to treatment was measured by means of both the Medication Event Monitoring System (MEMS) and pill count. Patients were followed-up for seven visits over a period of 1 year. At each visit to the physician's office, patient's adherence was assessed by both methods. RESULTS Adherence is defined as the percentage of days with correct dosing; median adherence according to MEMS was lower than median adherence according to pill count (91.6 vs. 96.1; P <0.001). Both methods agreed in defining patients as adherent in 107 (47%) and nonadherent in 33 (14%) patients. Thirty-one (14%) patients were adherent only by MEMS and 59 (25%) patients only by pill count. At the end of the study, patients in the four categories reached comparable blood pressure values and reductions. CONCLUSIONS Pill count could be a useful adjunct to electronic monitoring in assessing adherence patterns. Although deviant intake behavior occurred frequently, the effect on achieved blood pressure and blood pressure reduction was not remarkable.
Original languageEnglish
Pages (from-to)149-154
JournalAmerican Journal of Hypertension
Issue number2
Publication statusPublished - Feb 2010


  • adherence
  • blood pressure
  • compliance
  • hypertension
  • MEMS
  • pill count

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