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Resistant hypertension improved after 3 and 6 months by measuring drug levels to identify non-adherence.

Peeters, L., Kappers, M.H.W., Hesselink, D.A., Net, J.B. van der, Hartong, S.C.C., Bahmany, S., Massay, E., Dijk, L. van, Gelder, T. van, Koch, B.C.P., Versmissen, J. Resistant hypertension improved after 3 and 6 months by measuring drug levels to identify non-adherence. Journal of Hypertension: 2022, 40(Suppl. 1), p. e307-e308.
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Identification of non-adherence to antihypertensive drugs is crucial to improve resistant hypertension (RH). For this measuring drug levels is the most reliable method.

The primary objective of this analysis is to determine whether drug levels measured with a dried blood spot (DBS) sampling method combined with personalized feedback leads to a decrease in prevalence of RH after 3 and 6 months due to an increase in adherence.

Design and method
This is a multi-center single-blinded randomized controlled trial (RHYME-RCT, NL6736). Patients went to an eligibility visit, where DBS sampling and a 24-hour ambulatory blood pressure measurement (ABPM) was performed simultaneously. Patients with a daytime systolic blood pressure (SBP) > 135 and/or diastolic blood pressure (DBP) > 85 mmHg were randomized to standard treatment (control) or intervention. The intervention was performed by the treating physician and included information on drug levels and a personalized feedback conversation based on a feedback tool. The follow-up period was one year and included visits at 3, 6 and 12 months after the eligibility visit. At each visit an ABPM and DBS were performed.

A total of 78 patients (mean age of 59 ± 11 years, 75.6% male) with at least six months of follow-up were included. The prevalence of RH decreased from 100% in both arms to 60.0% in the intervention arm (p < 0.001, n = 35) and 58.1% in the control arm (p < 0.001, n = 43) after 6 months of follow-up. Adherence rates also improved over time, but only significantly improved in the intervention group after 3 months (p = 0.020). Furthermore, no statistically significant differences were found after six months between the two groups in the degree of RH (p = 0.868), SBP (p = 0.759) or adherence (p = 0.841).

Measuring blood pressure and drug levels led to a decrease in the prevalence of RH. However, this improvement could not be linked to the actual intervention or improvement of adherence.