Cost-effectiveness of enhancing adherence to therapy with blood pressure-lowering drugs in the setting of primary cardiovascular prevention

Prevalence and factors associated with adherence to anti-hypertensives among adults with hypertension in a developed Asian community: A cross-sectional study

Introduction:

Poor adherence to anti-hypertensive medications (AHM) results in hypertension treatment failure. Understanding and addressing the factors associated with adherence to AHM may potentially improve health outcomes. This study aimed to assess the prevalence and factors associated with patients’ adherence to AHM in a developed Asian community.

Methods:

An assistant-administered questionnaire survey was conducted on multi-ethnic Asian adults aged 31–80 years with essential hypertension based on their electronic health records (EHR) at a public primary-care clinic. Data on their demographic characteristics, clinical measurements of blood pressure and body mass index, co-morbidities and prescriptions from the EHR, along with the Medication Adherence Report Scale-5 scores were collated, audited and analysed. A MARS-5 score of <25 indicated poor adherence. Logistic regression was used to identify factors associated with adherence to AHM.

Results:

Data of 395 patients were analysed. Of these, 179 (45.3%) had poor adherence to at least one AHM. Bivariate analysis showed that poor adherence was significantly associated with lower mean age (59 years old vs. 63 years old), higher mean clinic diastolic blood pressure (76 mmHg vs. 73 mmHg) and higher mean weight (70.4 kg vs. 67.4 kg). Logistic regression showed that patients with no co-morbidities (such as diabetes mellitus, dyslipidaemia, stroke and ischaemic heart disease) had better medication adherence (MA; odds ratio=1.98; 95% confidence interval 1.14–3.45; p=0.02). There was no significant MA difference between the classes, dose frequency and number of AHM.

Conclusion:

Almost half of the patients had poor adherence to at least one AHM. Co-morbidity significantly influenced their MA. Attention should be directed to patients with co-morbidities to assess their AHM adherence.

Clinical Applicability of Monitoring Antihypertensive Drug Levels in Blood

Dried blood spot (DBS) analysis is a novel analytical method for therapeutic drug monitoring to identify nonadherence to antihypertensive drugs. This study was conducted to evaluate the clinical applicability of measuring drug concentrations of 8 antihypertensive drugs, using DBS and venipuncture. Furthermore, this study aimed to provide more insight into the between-patient variability in drug concentrations. False-negative values from DBS compared with a venipuncture were determined to assess drug adherence. A generalized estimating equation was used to estimate the model parameters, including sex, dose, age, weight, and the time interval, between drug intake and sampling, on the C_plasma (drug concentration in plasma). No false-negative values were found when measuring nonadherence using DBS compared with venipuncture. A high variability in C_plasma between patients was observed, especially at peak concentrations with a fold change reaching from 2.3 to 35.2. The time of intake was significantly related to the height of the C_plasma in 7 of the 8 measured drugs with a P<0.05, but the influence of dose, weight, age, and sex on drug levels differed largely between the measured drugs. DBS is a reliable and convenient method to assess nonadherence to antihypertensive drugs in clinical practice. The C_plasma of the 8 antihypertensive drugs in this study show a large interindividual difference, and therefore, low plasma concentrations do not necessarily mean nonadherence. Nonadherence can only be confirmed if drug levels are undetectable, that is, values below the lower limit of detection.

Fixed-Dose Triple Combination of Antihypertensive Drugs Improves Blood Pressure Control: From Clinical Trials to Clinical Practice

INTRODUCTION

Blood pressure (BP) control is the main clinical goal in the management of hypertensive patients; however, BP in most of these patients remains uncontrolled, despite the widespread availability of antihypertensive drugs as free-combination therapy. This study compared the efficacy of a fixed-dose triple combination (FDTC) of antihypertensive drugs with that of a free combination of three antihypertensives in patients with uncontrolled hypertension.

METHODS

Ninety-two patients (mean age 60.8 ± 12.1, 58.0% male) with uncontrolled essential hypertension (office systolic BP ≥ 140 or diastolic BP ≥ 90 mmHg) previously treated with a renin-angiotensin-aldosterone system (RAAS) inhibitor plus hydrochlorothiazide were switched to once-daily FDTC therapy with perindopril/indapamide/amlodipine (5-10/1.25-2.5/5-10 mg). Patients were age- and sex-matched with a control group of hypertensive patients receiving free-combination therapy with three drugs including a RAAS inhibitor, a diuretic, and a calcium channel blocker. Office BP and 24-h ambulatory BP monitoring (ABPM) were evaluated at baseline and after 1 and 4 months.

RESULTS

Significant reductions in ambulatory 24-h, daytime, and nighttime systolic BP, and pulse pressure (PP) were found in the FDTC group relative to reductions seen with free-combination therapy, after the first month only of follow-up. Target BP values (mean 24-h ambulatory systolic/diastolic BP < 130/80 mmHg) were reached by more recipients of FDTC than free-combination therapy (64.8% vs. 46.9%, p < 0.05) at month 4 of follow-up, despite reductions in 24-h ABPM values from baseline being similar in both groups at this time point.

CONCLUSION

FDTC of perindopril/indapamide/amlodipine was effective at reducing SBP and PP in previously treated patients with uncontrolled hypertension, and well tolerated, providing support for clinicians in choosing a fixed-dose triple combination over the free-combination of a RAAS inhibitor, a diuretic, and a calcium antagonist.

Free versus Fixed Combination Antihypertensive Therapy for Essential Arterial Hypertension: A Systematic Review and Meta-Analysis

Background

In a free drug combination, each Blood pressure (BP)-lowering drug is administered as a separate pill, while in a fixed drug combination several BP-lowering agents are combined in a single pill. Using a single pill may enhance compliance and simplify treatment, which would translate into better clinical outcomes. The objective of this meta-analysis is to compare the effects of using a fixed combination versus free combination of BP-lowering agents in the management of patients with essential hypertension.

Methods

We searched Cochrane CENTRAL, MEDLINE, and EMBASE for randomized clinical trials (RCTs) addressing the objective of the review and assessing at least one of the following outcomes: BP-lowering efficacy, rapidity in achieving BP target, compliance, incidence of side effects, mortality, and morbidity. Two review authors independently selected eligible studies, abstracted data, and assessed risk of bias of included trials. The primary meta-analyses used a random-effects model.

Results

We identified seven RCTs with a total of 397 participants. Meta-analysis of efficacy in controlling BP showed a non-significant reduction of mean systolic BP of 0.81 mmHg (95% CI -3.25, 1.64) favoring the fixed combination group. As for adverse events, results showed a non-significant 13% risk reduction favoring the free combination (risk ratio 1.13, 95% CI 0.85, 1.5). Low quality of evidence was noted for both outcomes. Rapidity in achieving BP target was assessed in only one trial, and the results favored the fixed combination. Adherence to treatment was assessed in three trials, no pooled analysis was possible for this outcome. None of the included trials assessed mortality and morbidity.

Conclusion

The available low quality evidence does not confirm or rule out a substantive difference between fixed combination and free combination therapy in the management of HTN. Well designed RCTs with a long duration of follow-up and assessment of morbidity and mortality outcomes are needed.

The association between adherence to cardiovascular medications and healthcare utilization

BACKGROUND

Poor adherence to medications for cardiovascular disease (CVD) is associated with adverse health outcomes, but little is known about its association with healthcare utilization (HCU).

OBJECTIVE

To examine whether adherence is associated with a long-term decrease in HCU.

METHODS

This is a retrospective cohort study of 1582 patients with CVD who enrolled in Maccabi Healthcare Services in Israel, initiating CVD medication therapy in 2006. Adherence was assessed by the proportion of days covered (PDC) with medications. Patients were defined as: non-adherent (PDC <0.4), partially adherent (0.4 ≤ PDC < 0.8), and fully adherent (PDC ≥0.8). HCU was estimated for 4 years following treatment initiation. Multivariable GEE models were used to analyze predictors of HCU. Model I included total adherence during the entire follow-up period as well as the interaction between this measure and the follow-up year. Model II included previous and current year's adherence as well as previous year's HCU cost. Both models were adjusted for potential confounders including: patient's age, gender, socioeconomic status, ownership of voluntary supplementary health insurance, and comorbidities.

RESULTS

The median age of patients was 63 (69 % males). Fifty-four percent of patients (n = 860) were defined as adherent, 24 % as partially adherent and 22 % as non-adherent. Model I: the annual HCU costs of adherent patients decreased by 10 % following treatment initiation [rate ratio (RR) = 0.90, 95 % confidence interval (CI) 0.86-0.94, P < 0.001]. This decrease stemmed predominantly from reduction in hospitalization costs. No significant changes in annual costs following treatment initiation were observed among partially adherent (RR = 1.00, 95 % CI 0.90-1.10, P = 0.935) and non-adherent (RR = 0.98, 95 % CI 0.87-1.10, P = 0.681) patients. Model II: no temporal association was found between adherence and HCU.

CONCLUSIONS

Adherence to CVD medications is relatively low. Adherence is associated with long-term decrease in healthcare expenditure. Exploring reasons for the high non-adherence and ways to improve adherence may optimize utilization of health systems' scarce resources.