Long-term persistence to mono and combination therapies with angiotensin converting enzymes and angiotensin II receptor blockers in Australia

Assuming one dose per day yields a similar estimate of medication adherence in patients with stroke: An exploratory analysis using linked registry data

PURPOSE

Prescribed daily dose (PDD), the number of doses prescribed to be taken per day, is used to calculate medication adherence using pharmacy claims data. PDD can be substituted by (i) one dose per day (1DD), (ii) an estimate based on the 75th percentile of days taken by patients to refill a script (PDD₇₅ ) or (iii) the World Health Organization's defined daily dose (DDD). We aimed to compare these approaches for estimating the duration covered by medications and whether this affects calculated 1-year adherence to antihypertensive medications post-stroke.

METHODS

We conducted a retrospective review of prospective cohort data from the ongoing Australian Stroke Clinical Registry linked with pharmacy claims data. Adherence was calculated as the proportion of days covered (PDC) for 1DD, PDD₇₅ and DDD. Differences were assessed using Wilcoxon rank-sum tests.

RESULTS

Among 12 628 eligible patients with stroke, 10 057 (80%) were prescribed antihypertensive medications in the year after hospital discharge (78.2% aged ≥65 years, 45.2% female). Overall, the 75th percentile of patient time until next medication refill was 39 days. The greatest variations in dose regimens, estimated using person- and dose-level refill times, were for beta blockers (11.4% taking two tablets/day). There were comparable levels of adherence between 1DD and the PDD₇₅ (median PDC 91.0% vs 91.2%; P = 0.70), but adherence was slightly higher using DDD (92.3%; both P < 0.001). However, this would represent a clinically nonsignificant difference.

CONCLUSION

Adherence to antihypertensive medications shows similar estimates across standard measures of dosage in patients during the first year after an acute stroke.

Fixed dose drug combinations - are they pharmacoeconomically sound? Findings and implications especially for lower- and middle-income countries

Introduction: There are positive aspects regarding the prescribing of fixed dose combinations (FDCs) versus prescribing the medicines separately. However, these have to be balanced against concerns including increased costs and their irrationality in some cases. Consequently, there is a need to review their value among lower- and middle-income countries (LMICs) which have the greatest prevalence of both infectious and noninfectious diseases and issues of affordability.Areas covered: Review of potential advantages, disadvantages, cost-effectiveness, and availability of FDCs in high priority disease areas in LMICs and possible initiatives to enhance the prescribing of valued FDCs and limit their use where there are concerns with their value.Expert commentary: FDCs are valued across LMICs. Advantages include potentially improved response rates, reduced adverse reactions, increased adherence rates, and reduced costs. Concerns include increased chances of drug:drug interactions, reduced effectiveness, potential for imprecise diagnoses and higher unjustified prices. Overall certain FDCs including those for malaria, tuberculosis, and hypertension are valued and listed in the country's essential medicine lists, with initiatives needed to enhance their prescribing where currently low prescribing rates. Proposed initiatives include robust clinical and economic data to address the current paucity of pharmacoeconomic data. Irrational FDCs persists in some countries which are being addressed.

Antihypertensive polytherapy in Australia: prevalence of inappropriate combinations, 2013-2018

OBJECTIVES

To estimate the prevalence of inappropriate antihypertensive polytherapy in Australia.

METHODS

We used a nationally representative 10% sample of Pharmaceutical Benefits Scheme (PBS) eligible Australians and their dispensing history to identify people aged 18+ years exposed to at least one PBS-listed antihypertensive between 2012 and 2018. We measured prevalence of antihypertensive polypharmacy (≥40 days concomitant exposure), inappropriate antihypertensive combinations (against guideline recommendations; within-class polytherapy) and combinations to be used with caution.

RESULTS

Almost half (47.5%) of people using antihypertensives in 2018 experienced polytherapy. Among these, 2.4% had an inappropriate combination (1.5% against guidelines; 1.0% within-class polytherapy). Inappropriate combinations were more prevalent in people experiencing polytherapy with three (3.7%) or four (16.1%) antihypertensive medicines than people on dual therapy (0.7%). Inappropriate combinations occurred at a lower rate in people using fixed-dose rather than free-drug combinations for dual therapy (0 vs. 0.7%) and in those using three antihypertensives (2.4 vs. 7.3%); this was not the case for people using four or more antihypertensives (15.5 vs. 16.1%). Between 2013 and 2018, the prevalence of antihypertensive polytherapy was relatively stable (49-47%); however, the prevalence of inappropriate combinations among these patients halved (from 5.1 to 2.4%).

CONCLUSION

Antihypertensive polytherapy in Australia is common, but the prevalence of inappropriate combinations is low and decreasing over time, suggesting strong awareness of Australian clinical guidelines. However, in 2018, approximately 49 000 Australian adults experienced inappropriate polytherapy; prescribing of fixed-dose combinations in patients on dual or triple therapy may further reduce this inappropriate care, although increased vigilance treating patients with more than 3 antihypertensives is required.

Operationalization and validation of a novel method to calculate adherence to polypharmacy with refill data from the Australian pharmaceutical benefits scheme (PBS) database

Background

Electronic health care data contain rich information on medicine use from which adherence can be estimated. Various measures developed with medication claims data called for transparency of the equations used, predominantly because they may overestimate adherence, and even more when used with multiple medications. We aimed to operationalize a novel calculation of adherence with polypharmacy, the daily polypharmacy possession ratio (DPPR), and validate it against the common measure of adherence, the medication possession ratio (MPR) and a modified version (MPR_m).

Methods

We used linked health data from the Australian Pharmaceutical Benefits Scheme and Western Australian hospital morbidity dataset and mortality register. We identified a strict study cohort from 16,185 patients aged ≥65 years hospitalized for myocardial infarction in 2003–2008 in Western Australia as an illustrative example. We applied iterative exclusion criteria to standardize the dispensing histories according to previous literature. A SAS program was developed to calculate the adherence measures accounting for various drug parameters.

Results

The study cohort was 348 incident patients (mean age 74.6±6.8 years; 69% male) with an admission for myocardial infarction who had cardiovascular medications over a median of 727 days (range 74 to 3,798 days) prior to readmission. There were statins (96.8%), angiotensin converting enzyme inhibitors (88.8%), beta-blockers (85.6%), and angiotensin receptor blockers (13.2%) dispensed. As expected, observed adherence values were higher with mean MPR (median 89.2%; Q₁: 73.3%; Q_3: 104.6%) than mean MPR_m (median 82.8%; Q₁: 68.5%; Q_3: 95.9%). DPPR values were the most narrow (median 83.8%; Q₁: 70.9%; Q_3: 96.4%). Mean MPR and DPPR yielded very close possession values for 37.9% of the patients. Values were similar in patients with longer observation windows. When the traditional threshold of 80% was applied to mean MPR and DPPR values to signify the threshold for good adherence, 11.6% of patients were classified as good adherers with the mean MPR relative to the DPPR.

Conclusion

In the absence of transparent and standardized equations to calculate adherence to polypharmacy from refill databases, the novel DPPR algorithm represents a valid and robust method to estimate medication possession for multi-medication regimens.

EFFICACY AND SAFETY OF A SINGLE-PILL COMBINATION OF ATORVASTATIN/AMLODIPINE IN PATIENTS WITH ARTERIAL HYPERTENSION AND DYSLIPIDEMIA

- The aim was to evaluate the efficacy of a single-pill combination of atorvastatin/amlodipine in patients with arterial hypertension, dyslipidemia and moderate to high cardiovascular risk. This prospective study included 243 patients with arterial hypertension, dyslipidemia and moderate to high cardiovascular risk, mean age 63.3±9.8 years. All patients were prescribed a treatment with one of the following doses of a single-pill combination of atorvastatin/amlodipine: 10/5, 10/10, 20/5 or 20/10 mg daily. The follow-up period was 3 months. The mean baseline values of the systolic and diastolic blood pressure were 155.7±16.2 and 92.0±9.2 mm Hg, respectively. At month 3, the respective mean systolic and diastolic blood pressure values were 136.9±26.9 and 80.6±5.1 mm Hg. The mean baseline values of total cholesterol and low-density lipoprotein cholesterol were 6.6±1.2 and 4.4±1.1 mmol/L, respectively. At month 3, the respective mean values of total cholesterol and low-density lipoprotein cholesterol were 5.1±0.9 and 2.9±1.0 mmol/L. Treatment was discontinued in 9 (3.7%) patients due to adverse events. In conclusion, treatment with the single-pill combination of atorvastatin/amlodipine was effective and well tolerated by the patients with arterial hypertension, dyslipidemia and moderate to high cardiovascular risk.

Does a fixed-dose combination of amlodipine and atorvastatin improve persistence with therapy in the Australian population?

AIM

To compare persistence in people who initiate the combination of amlodipine and statin as a fixed-dose combination (FDC) or separate pill combination (SePC), and assess the impact of prior medicine exposure on this outcome.

METHOD

Prescription dispensing data from a national administrative dataset was used to identify patients initiating FDCs or SePCs of amlodipine and statin between April and September 2013. Each cohort was stratified according to dispensing of calcium channel blockers (CCBs) or statins in the prior 12 months. Time to cessation of combination therapy (persistence) was analyzed over 12 months using Kaplan Meyer survival analysis and Cox proportional hazards (PH) models. Patient factors associated with length of treatment were identified using Cox PH modeling.

RESULTS

Of 26,000 people who initiated combination amlodipine and statin, the majority initiated SePCs (77%). The unadjusted cessation rates at 12 months were SePC 40% and FDC 44%. Following adjustment for patient factors, the risk of ceasing combination therapy was higher in those taking the SePC versus FDC, hazard ratio (95% CI): 1.15 (1.11, 1.21). Patients naïve to both therapies had double the cessation rate compared to those who had at least one prior dispensing of a statin. Factors positively associated with persistence were prior use of other antihypertensive drugs and reaching the medicine subsidy safety-net: factors that were more common in users of SePC amlodipine and statin.

CONCLUSION

In this study we found a lower risk (15%) of ceasing combination therapy when people initiate amlodipine and statin in the form of a FDC. While this outcome supports findings in other countries that FDCs improve persistence with combination therapy, prior experience with component or similar medicines has a larger impact on persistence regardless of formulation initiated.

Prior experience with cardiovascular medicines predicted longer persistence in people initiated to combinations of antihypertensive and lipid-lowering therapies: findings from two Australian cohorts

PURPOSE

Many studies of persistence involving fixed dose combinations (FDCs) of cardiovascular medicines have not adequately accounted for a user's prior experience with similar medicines. The aim of this research was to assess the effect of prior medicine experience on persistence to combination therapy.

PATIENTS AND METHODS

Two retrospective cohort studies were conducted in the complete Pharmaceutical Benefits Scheme prescription claims dataset. Initiation and cessation rates were determined for combinations of: ezetimibe/statin; and amlodipine/statin. Initiators to combinations of these medicines between April and September 2013 were classified according to prescriptions dispensed in the prior 12 months as either: experienced to statin or calcium channel blocker (CCB); or naïve to both classes of medicines. Cohorts were stratified according to formulation initiated: FDC or separate pill combinations (SPC). Cessation of therapy over 12 months was determined using Kaplan-Meier survival analysis. Risk of cessation, adjusted for differences in patient characteristics was assessed using Cox proportional hazard models.

RESULTS

There were 12,169 people who initiated combinations of ezetimibe/statin; and 26,848 initiated combinations of amlodipine/statin. A significant proportion of each cohort were naïve initiators: ezetimibe/statin cohort, 1,964 (16.1%) of whom 81.9% initiated a FDC; and amlodipine/statin cohort, 5,022 (18.7%) of whom 55.4% initiated a FDC. Naïve initiators had a significantly higher risk of ceasing therapy than experienced initiators regardless of formulation initiated: ezetimibe/statin cohort, naïve FDC versus experienced FDC HR=3.0 (95% CI 2.8, 3.3) and naïve SPC versus experienced SPC HR=4.4 (95% CI 3.8, 5.2); and amlodipine/statin cohort naïve FDC versus experienced FDC HR=2.0 (95% CI 1.8, 2.2) and naïve SPC versus experienced SPC HR=1.5 (95% CI 1.4, 1.6).

CONCLUSION

Prescribers are initiating people to combinations of two cardiovascular medicines without prior experience to at least one medicine in the combination. This is associated with a higher risk of ceasing therapy than when combination therapy is initiated following experience with one component medicine. The use of FDC products does not overcome this risk.