Copayment Burden Affects Medication Adherence in Chronic Conditions

Copayments may be a structural barrier to pulmonary vasodilator therapy adherence, with an association between higher copayments and medication adherence in adults receiving prostanoids and combination therapy for pulmonary arterial hypertension (PAH).

Copayments can be a barrier to medication adherence in PAH. | Image credit: Ahmad - stock.adobe.com

Although randomized controlled trials have demonstrated multiple benefits associated with endothelin receptor antagonists (ERA) and phosphodiesterase type-5 (PDE5) inhibitors combination therapy vs monotherapy, the economic burden of this treatment is substantial, with mean estimated costs topping $4500 per month.1

Due to the high costs of these medications, investigator used administrative claims data from insured individuals to evaluate the way in which medication copayment and household income relate to medication adherence in PAH. Study data were collected from Optum’s deidentified Clinformatics Data Mart, and patients with a PAH diagnosis made between 2015 and 2020 were included in the study. Participants were categorized by medication class, and combination therapy was defined by overlapping pharmacy claims for ERAs and PDE5s for 90 days or longer without discontinuation of either medication during the study period.

The primary study outcome was medication adherence measured by estimated proportion of days covered.

READ MORE: FDA Grants Tentative Approval to Treprostinil for PAH Associated with PH-ILD

The final study cohort included 4025 patients (mean age, 65.9±13.3 years; 71.2% women, 51.6% white); comorbidities included hypertension, chronic pulmonary disease, congestive heart failure, diabetes, and valvular disease. Socioeconomically, 43.6% had attained some level of college education, and 23.7% had a household income greater than $75,000. The majority of the cohort—79%—included Medicare beneficiaries.

The median 30-day copayment was $45.25 for ERAs, $11.05 for PDE5, $60.08 for prostanoids, $45.00 for soluble guanylate cyclase stimulators, and $31.60 for combination therapy. Investigators noted that distributions were skewed across medication classes due to the presence of outliers with high copayments.

In a fully adjusted multivariable analysis, investigators observed decreased odds of achieving proportion of days covered of 80% or greater among individuals with high copayments for prostanoid medications and combination therapy (OR, 0.36; 95% CI, 0.20-0.65 and OR, 0.61; 95% CI, 0.38-0.97) relative to those with low copayments. High copayments were associated with nearly 2-fold higher odds of reaching proportion of days covered of 80% or higher for PDE5s (OR, 1.86; 95% CI, 1.34-2.59).

When comparing household income, there were no significant differences between those with an annual household income of $75,000 or higher, less than $40,000, or between $40,000 and $74,999 in terms of medication adherence to either mono- or combination therapy. Findings remained similar in subgroup analyses, which included only 3735 participants with 12 or more months of continuous enrollment following first medication fill.

The Role of the Pharmacist

In addition to cost considerations, research has shown that the adverse effects of PAH treatment “make it challenging to motivate patients to follow the prescribed treatment plan over time,” with adherence as low as 50% according to some studies.²

However, as with many other chronic conditions, pharmacists can play a vital role in ensuring patient medication adherence. According to a 2019 study published in PLoS One,³ patients who received phosphodiesterase-5 inhibitor therapy through an integrated, multidisciplinary care model that included clinical specialty pharmacists were significantly more likely to achieve high medication adherence rates and experience lower out of pocket medication costs. Another study, published in ERJ Open Research,² showed that the integration of a pharmacology specialist in the outpatient setting is also correlated with increased treatment adherence.

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References

1. Schikowski EM, Swabe G, Chan SY, Magnani JW. Association between copayment and adherence to medications for pulmonary arterial hypertension. J Am Heart Assoc. 2022;11(22):e025520. Doi:10.1161/JAHA.122.026620

2. Kjellström B, Sandqvist A, Hjalmarsson C, et al. Adherence to disease-specific drug treatment among patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. ERJ Open Res. 2020;6(4):00299-2020. Doi:10.1183/23120541.00299-2020

3. Shah NB, Mitchell RE, Proctor ST, et al. High rates of medication adherence in patients with pulmonary arterial hypertension: an integrated specialty pharmacy approach. PLoS One. 2019;14(6):e0217798. Doi:10.1371/journal.pone.0217798