Resistant hypertension is common among the hypertensive population with reported prevalence of 12 to 15%. These patients have a higher cardiovascular risk and consequently a poorer cardiovascular prognosis. Suboptimal adherence with antihypertensive medication is a common contributing factor in apparent treatment-resistant hypertension. Patients were observed taking their medications under direct supervision at our directly observed therapy (DOT) clinic. At the DOT clinic visit, patients were fitted with a 24-h ambulatory blood pressure (ABP) monitor and each drug, at currently prescribed dose, was administered by a nurse; at an hourly interval and patient observed for 7 h. ABP readings between pre and post DOT clinic were compared. Fifty out of 56 patients had complete data on the ABP. Twenty four were female and the mean (s.d.) age was 62.0 (11.0) years. On the basis of the study methods that differentiated patients according to their BP response during the DOT clinic, twenty-five (50.0%) patients were deemed to be truly resistant (24-h ambulatory systolic blood pressure (SBP) fall <5 mm Hg) and the remaining 25 were deemed to have clinically significant non-adherence (24-h ambulatory SBP fall ⩾5 mm Hg) to prescribed therapy. In non-adherent patients, the mean 24-h ambulatory BP drop observed was 19.5/9.4 mm Hg (P<0.001 for both). Our results suggest that non-adherence is very common among patients considered to have apparent treatment-resistant hypertension. DOT clinic can be an effective method of identifying the truly resistant hypertensive patients.
Nonadherence is a common reason for treatment failure and treatment resistance. No matter how it is defined, it is a major issue in the management of chronic illnesses. There are numerous methods to assess adherence, each with its own strengths and weaknesses; however, no single method is considered the best. Nonadherence is common in patients with hypertension, and it is present in a large proportion of patients with uncontrolled blood pressure taking three or more antihypertensive agents. Availability of procedure-based treatment options for these patients has shed further light on this important issue with development of new methods to assess adherence. There is, however, no consensus on the management of nonadherence, which reflects the complex interplay of factors responsible for it.
Objective: Non-adherence to medication is present in ≥50% of patients with apparent treatment resistant hypertension. We examined the factors associated with non-adherence as detected by an LC-MS/MS based urine antihypertensive drug assay.Methods: All urine antihypertensive test results, carried out for uncontrolled hypertension (BP persistently >140/90 mmHg) between January 2015 and December 2016 at a single toxicology laboratory were analysed. Drugs detected were compared to the antihypertensive drugs prescribed. Patients were classified as adherent (all drugs detected), partially nonadherent (≥1 prescribed drugs detected) or completely non-adherent (no drugs detected).Demographic and clinical parameters were compared between the adherent and non-adherent groups. Binary logistic regression analysis was performed to determine association between non-adherence and demographic and clinical factors.Results: Data on 300 patients from 9 hypertension centres across the UK were analysed. The median age was 59 years, 47% female, 71% Caucasian , median clinic BP was 176/95 mmHg and the median number of antihypertensive drugs prescribed was four. One hundred and sixty-six (55%) were non-adherent to prescribed medication with 20% of these being completely non-adherent. Non-adherence to antihypertensive medication was independently associated with younger age, female gender, number of antihypertensive drugs prescribed, total number of all medications prescribed (total pill burden) and prescription of a calcium channel blocker.
Conclusion:This LC-MS/MS urine analysis-based study suggests the majority of patients with apparent treatment resistant hypertension are non-adherent to prescribed treatment.Factors that are associated with non-adherence, particularly pill burden, should be taken into account while treating these patients.
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