Directly Observed Therapy in Treatment Resistant Hypertension – A Pilot Study

B Griffin1, IM MacIntyre1,2, EE Morrison1, DJ Webb1, D Begg2. 1University of Edinburgh, Edinburgh, UK, 2NHS Lothian, Edinburgh, UK

Introduction: Treatment resistant hypertension (TRH) is defined as the failure to achieve a blood pressure target of <140/90 mmHg in patients with hypertension, despite adherence to a treatment regimen of at least 3 antihypertensive medications at optimal tolerated doses, preferably including a diuretic 1. The exact prevalence of TRH is unknown, yet estimates can be derived from retrospective, cross-sectional population studies and are of around 12%. However, with mean drug adherence to antihypertensive medication estimated to be only 57%, and a clinician’s ability to diagnose non-adherence described previously as no better than a coin toss, the question of drug adherence in this patient group is an important one. Our aim was to investigate the efficacy of non-adherence questionnaires to identify adherence issues and establish whether a significant difference in clinic BP results exists following directly observed therapy (DOT) within the presumed resistant hypertensive population.

Method: 18 patients with resistant hypertension were randomly identified using a general practice database and 2 were excluded due to frailty. Patients were consented, completed an adherence questionnaire and underwent directly observed therapy (DOT) immediately before undertaking ambulatory blood pressure monitoring (ABPM). The ABPM procedure was unchanged from local practice.

Results: All 16 patients approached consented to the study. Overall there was a significant fall in both systolic and diastolic BP following ABPM (-23 mmHg and -18mmg respectively, p <0.005). 3/16 (19%) patients admitted to not taking the medication correctly when they took part in the drug amnesty. A further 2/16 (13%) patients appeared to be over-treated, on the basis of a large fall in BP, when supervised consumption occurred (these patients did not admit in the amnesty to not taking medication.) This implies that up a third of patients in this cohort may not have been taking their medication as prescribed and could be identified by the supervised consumption process. All patients found completing the adherence questionnaire, and undertaking DOT, acceptable.

Conclusion: Non-adherence to medication likely plays a large contributing role in resistant hypertension, which is then not truly TRH. Strategies to identify this issue are crucial to good hypertension management in terms of achieving treatment goals and avoiding the prescription of wasted medicines. This pilot data is being used to inform a large randomised control trial studying DOT within the resistant hypertension patient population, aiming to inform our approach to its diagnosis and management.

References

(1) Calhoun DA, et al. Resistant hypertension: diagnosis, evaluation, and treatment: a scientific statement from the American Heart Association Professional Education Committee of the Council for High Blood Pressure Research. Circulation. 2008;117:e510-526

(2) de la Sierra A, et al. Clinical features of 8295 patients with resistant hypertension classified on the basis of ambulatory blood pressure monitoring. Hypertension. 2011;57:898-902

(3) Persell SD. Prevalence of resistant hypertension in the United States, 2003-2008. Hypertension. 2011;57:1076-1080