Adherence with levodopa/carbidopa/entacapone versus levodopa/carbidopa and entacapone as separate tablets in patients with Parkinson’s disease

Abstract

Background:

Observational studies suggest that single-tablet formulations are associated with improved adherence versus the same components taken as separate tablets. The objective of this study was to compare adherence in patients with Parkinson’s disease (PD) receiving levodopa therapy as levodopa/carbidopa/entacapone tablets (LCE) versus levodopa/carbidopa (LC) tablets and entacapone (E) as separate tablets (LC and E).

Methods:

This was a retrospective, observational cohort study using a large health insurance claims database. Subjects included persons with a PD diagnosis who were receiving LC without E and then received either an add-on therapy with E as a separate tablet (LC and E) or LCE as one tablet (LCE). The primary study outcome was treatment adherence, estimated from pharmacy refills based on the ‘percent of days covered’ (PDC) with LCE or LC and E during follow-up and compared for patients receiving LCE and LC and E using multivariate regression analyses.

Results:

In multivariate analyses controlling for differences between groups in baseline characteristics, including pre-index dosage of and adherence with LC, receipt of LCE (n = 388) was associated with 79% lower mean non-adherence during follow-up (95% CI: 73–83%; p < 0.001) versus LC and E (n = 823), 86% lower odds of unsatisfactory adherence (95% CI: 80–91%; p < 0.001), and a 26% lower risk of discontinuation (95% CI: 6–42%; p < 0.013).

Limitations:

This was an observational study with the inherent potential for selection bias. Pharmacy claims may not provide an accurate estimate of adherence. Requiring subjects to have a certain number of prescriptions before and after the index date may yield a sample that is not representative of all patients initiating levodopa therapy in typical clinical practice.

Conclusions:

Better adherence with LCE may have important implications for maintaining function in patients receiving chronic oral levodopa therapy. Further research is needed to confirm these results and examine the association between improved adherence and clinical and economic outcomes.

Keywords::

• Adherence
• Motor complications
• Parkinson’s disease
• Wearing-off

Transparency

Declaration of funding

Funding for this study was provided to Policy Analysis Inc. (PAI), an independent contract research organization, by Novartis. Novartis also funded the manuscript preparation.

Declaration of financial/other relationships

T.D. and M.H. are employees of PAI, which has received research support and consulting fees from Novartis and other pharmaceutical companies. T.D. has received honoraria from Novartis. S.K.T. and L.M. are employees of Novartis, and own stock/options in Novartis.

Peer reviewers may receive honoraria from CMRO for their review work. The peer reviewers have disclosed no relevant financial relationships.

Acknowledgments

Editorial assistance was provided by Meghan E. Gallagher. Funding for the editorial assistance was provided by Novartis.

Notes

*Stalevo is a registered trade name of Orion Pharma, Espoo, Finland.

†MarketScan is a registered trade name of Thomson Reuters.

*SAS is a registered trade name of SAS Institute Inc., Cary, NC, USA.