Antihypertensive use before and after initiation of fixed-dose combination products in Australia: a retrospective study

Are We There Yet? Exploring the Use of Single-Pill Combination Therapy in the Management of Raised Blood Pressure in Australia

OBJECTIVE

Single-pill combination (SPC) therapy is recommended as first-line therapy for most patients in global hypertension guidelines due to benefits of improved adherence and blood pressure (BP) control. We aimed to understand factors affecting SPC use in the management of raised BP in Australia.

DESIGN

A mixed-method study comprising of qualitative (policy review and interviews) and quantitative (Pharmaceutical Benefits Scheme [PBS] data) approaches.

MAIN OUTCOME MEASURES

Australian and international hypertension guideline recommendations regarding SPC use; the Australian registration and subsidy approval processes of SPCs; use of SPCs on the PBS; cost-analysis of PBS-listed SPCs compared to free-drug combinations; perceptions of healthcare providers towards SPCs.

RESULTS

The 2016 Australian Heart Foundation's "Guideline for the diagnosis and management of hypertension in adults" does not recommend combination therapy (including SPCs) as first-line treatment. Additional challenges in the uptake of SPCs include: (1) the additional PBS requirements and barriers imposed for the listing of SPCs. (2) Script volumes for SPCs have not matched the rise in the number of SPCs listed for subsidy, have plateaued since 2016 and remained significantly lower than single constituent scripts. (3) SPCs are not subsidised by the PBS for initial treatment. Most SPCs provided substantial cost savings for individual patients compared to free-drug combinations. Health care providers were positive about the cost-saving and convenience of SPCs, however perceived negatives included inflexibility of SPCs during dose titration, medicine shortages, and potential adverse effects when initiating treatment with multiple drugs.

CONCLUSION

The safety, efficacy and cost-saving potential of SPCs have been established in the literature but several roadblocks in the existing health system in Australia impede uptake. Interventions addressing these barriers may facilitate improved uptake, which may in turn improve blood pressure control in Australia.

Can patterns of medication use explain the increasing incidence of end stage kidney disease among people with diabetes in Australia?

AIMS

Recently, an increase in the incidence of end-stage kidney disease (ESKD) among people with type 2 diabetes (T2D) aged < 50 years and ≥ 80 years has been observed in Australia. We examined whether patterns of medication use are likely to explain these trends.

METHODS

Among National Diabetes Services Scheme registrants, we determined the annual prevalence of dispensed glucose-lowering (GL), blood-pressure-lowering (BPL) and lipid-lowering (LL) agents with ≥3, ≥6 or ≥9 dispensings per year from 2003 to 2013. Relative changes in the prevalence were determined via Poisson regression.

RESULTS

During 2003-2013, the percentage of people with T2D dispensed GL, BPL and LL agents with ≥3, ≥6 or ≥9 dispensings per year increased in all age-groups. From 2003 to 2013, GL, BPL and LL agents use with ≥3 dispensings per year increased by 17%, 8.2%, and 53%, respectively. The use of renin-angiotensin-aldosterone-system-blockers over time also increased but more slowly in those aged <60 years compared to those aged ≥80 years (6% vs 18%, p < 0.001).

CONCLUSIONS

Changes in medication use are not likely to explain increasing incidence of ESKD in younger Australians with T2D. Studies are needed to provide insights into the major drivers of the rising incidence of ESKD in this population.

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.

Dispensing Patterns of Blood Pressure Lowering Agents in Older Australians From 2006 to 2016

BACKGROUND

Increasing numbers of blood pressure lowering (BPL) agents are being prescribed for both primary and secondary prevention of cardiovascular disease, especially in the older population. The aim of this study is to describe the temporal trends and patterns of BPL dispensing among older Australians (aged ≥65 years).

METHODS

We utilized prescription claims data from the Australian Pharmaceutical Benefits Scheme (PBS) for a 10% random sample of people aged ≥65 years. The PBS, funded by the Federal government, provides subsidies to make medicines more affordable for Australian residents. We restricted our analysis to "long-term concession" individuals, who would use PBS for the majority of their medication needs. BPL agents were identified using the World Health Organization Anatomical Therapeutic Chemical classification codes. The annual prevalences and proportional distributions of BPL dispensing by categories were summarized from 2006 to 2016. Direct standardization was applied to indicate changes of BPL dispensing over time.

RESULTS

Age-standardized dispensing of BPL agents increased by 8% among older Australians from 2006 to 2016 (58%-66%). BPL dispensing in males has exceeded that in females since 2009. Angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers were the dominant BPL agents dispensed, with more than 55% of all BPL users over time. Dispensing of diuretics decreased from 27% to 21%, calcium channel blockers decreased from 30% to 25%, while β-blockers remained stable (29%-31%). The use of fixed-dose combinations increased over time from 23% to 31%.

CONCLUSION

The prevalence of BPL dispensing steadily increased among older Australians from 2006 to 2016. The changes in the patterns of BPL dispensing were largely in line with contemporary changes to clinical guidelines for an aging population.

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.

How does prescribing for antihypertensive products stack up against guideline recommendations? An Australian population-based study (2006-2014)

AIMS

We describe choice of first-line antihypertensive drug therapy and uptake of fixed-dose combinations (FDCs) in Australia, and investigate the impact of initiation on FDCs and other non-recommended first-line therapies on treatment discontinuation.

METHOD

This was a population-based retrospective cohort study using a random 10% sample of persons dispensed an Australian Pharmaceutical Benefits Scheme listed medicine from 1 July 2005 to 30 June 2014. The primary outcomes were adherence to Australian recommendations at initiation of antihypertensive therapy, discontinuation of initial therapy and discontinuation of any therapy in the first year after initiation.

RESULTS

In our sample of 55 937 persons initiating therapy, 42.0% did so outside Australian recommendations, including not initiating on recommended monotherapy (26.3%) and not initiating on the lowest recommended dose (30.6%). Only 1.7% of individuals who were dispensed an FDC established therapy on the free combination regimen (as recommended) prior to switching. After adjusting for covariates, persons initiating on non-recommended monotherapy (OR = 2.64, 95% CI 2.47-2.83) or FDCs of two or more antihypertensives (OR = 1.42, 95% CI 1.30-1.55), were more likely to discontinue all antihypertensive drug treatment in the first year compared to persons initiating on recommended monotherapy.

CONCLUSION

More than half of antihypertensive initiators conformed to Australian guidelines. Initiation on FDCs and other non-recommended treatments was associated with lower persistence on antihypertensive therapy in the first year. Long-term effectiveness and outcomes may be enhanced by initiating with low dose monotherapy.