Medication adherence in patients with apparent resistant hypertension: findings from the SYMPATHY trial.

Abstract

Introduction

Hypertension is only controlled in approximately 35% of the patients, which could be partially due to non-adherence. Recently, bioanalytical assessment of adherence to blood pressure (BP) lowering drugs has gaining interest. Our aim was to explore possible determinants of non-adherence in treatment resistant hypertension, assessed by objective screening for antihypertensive agents in serum. Secondary aim was to study the effect of adherence on the change in BP.

Methods

This project was a sub-study of SYMPATHY; an open-label randomized-controlled trial to assess the effect of renal denervation on BP six months after treatment compared to usual care in patients with resistant hypertension. Stored serum samples were screened for antihypertensive agents to assess adherence at baseline and six months after intervention, using liquid chromatography-tandem mass spectrometry. Office and 24-hour BP were measured at the same day blood was sampled. Patients and physicians were unaware of adherence measurements.

Results

Ninety-eight baseline and 83 six-month samples were available for analysis. Sixty-eight percent (95%CI 59 to 78) of the patients was non-adherent (n=67). For every 1 pill more prescribed, 0.785 [95%CI 0.529 to 0.891] prescribed pill was less detected in blood. A decrease of 1 pill in adherence between baseline and six months was associated with a significant rise in office systolic BP of 4 (95%CI 0.230 to 8.932) mmHg.

Conclusion

Objective measurement of BP lowering drugs in serum, as a tool to assess adherence, showed that non-adherence was very common in patients with apparent resistant hypertension. Furthermore, the assessment results were related to (changes in) blood pressure. Our findings provide direct and objective methodology to help the physician to understand and to improve the condition of apparent resistant hypertension.

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