Adherence to drug regimens may increase with generics

Take-Home Message: The costs associated with medications for patients with glaucoma continue to have a significant effect on adherence. Making a switch from branded to generic drugs may make a difference for some patients in certain cases.

By Lynda Charters; Reviewed by Joshua Stein, MD, MS

Ann Arbor, MI-Adherence to medication can be a major challenge for patients with glaucoma, with any number of reasons for why patients struggle with their regimens, said Joshua Stein, MD, MS.

One of the major factors is medication cost, said Dr. Stein, associate professor, Department of Ophthalmology and Visual Sciences, University of Michigan, and director, Center for Eye Policy and Innovation, Ann Arbor.

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Quantifying the impact of cost on adherence can be difficult. Patients can be too embarrassed to admit to the financial burden imposed by the drug regimen, either when filling out research surveys or when participating in focus groups, Dr. Stein explained.

Prostaglandin analogues-among the most frequently prescribed and most effective drugs to treat open-angle glaucoma-require only once-daily dosing and have minimal side effects. However, they are also among the most expensive of the glaucoma drugs.

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“Some patients pay over $100 out of pocket each month,” Dr. Stein said.

Next: Availability of latanoprost

The financial burden for some patients saw a considerable potential reduction in 2011, when the first generic prostaglandin analogue, i.e., latanoprost, became commercially available in the United States.

In light of this, Dr. Stein and colleagues conducted a study to determine if the availability of latanoprost for open-angle glaucoma had an effect on patient adherence. Namely, was there an impact to patients’ drug regimens after they switched from a brand-name drug to the generic version, compared with other patients with glaucoma who continued taking a brand-name prostaglandin analogue?

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Investigators evaluated data from a large, managed-care database of patients aged 40 years and older who received a diagnosis of open-angle glaucoma and were followed in the plan from September 2009 to December 2012. All patients in the medical plan were also enrolled in the pharmacy plan.

Patients had at least one record of a prescription for a brand-name prostaglandin analogue before 2009. The study thus avoided patients who were newly treated during the first 18 months of the study period.

All patients were taking a brand-name prostaglandin analogue before the generic version of Xalatan (latanoprost) became available. Patients were excluded if they had undergone a surgery or laser treatment for glaucoma.

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Investigators defined improved adherence to medication as an increase of 25% or more in the proportion of days covered by a drug and worsening adherence as a decrease of 25% or more, he explained.

A total of 8,427 patients met the study inclusion criteria, with more than 2,000 patients taking each of the three brand-name medications-Xalatan, Pfizer Pharmaceuticals; bimatoprost (Lumigan, Allergan); and travoprost (Travatan Z, Alcon Pharmaceuticals)-before the introduction of generic latanoprost to the market.

Next: Improved adherence

There was little change in the rates of medication adherence among patients who continued taking a brand-name product after the generic became available, Dr. Stein noted.

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“However, for a subset of patients who were switched to generic latanoprost, adherence to their initially prescribed, brand-name drug was lower than average, yet subsequently increased substantially after the switch to the generic product,” he said.

Improved adherence

Of special interest were factors identified by regression analysis that were associated with improved adherence. Results showed that patients remaining on a brand-name drug had a 28% reduced odd of improved adherence and a 39% higher odd of worsening of adherence.

Factors associated with improved adherence include use of generic latanoprost in the post-introductory period, higher insurance co-payments in the pre-generic period, lower insurance co-payments in the post-generic period, and black race.

Variables associated with reduced rates of adherence include use of brand-name drugs throughout the study period, higher monthly insurance co-payments in the post-introductory period, black race, and a lack of visits to eye-care providers.

Next: "This may be particularly helpful for patients"

Dr. Stein and co-investigators suggest ophthalmologists consider switching treatments for patients who are not adhering to their glaucoma-medication regimens to a generic product, if possible.

“This may be particularly helpful for patients with high medication co-payments and for patients from racial minority groups,” he said. “Such persons may discontinue use of their medical glaucoma treatment altogether if they simply cannot afford the medications they are prescribed.”

Joshua Stein, MD, MS

E: jdstein@med.umich.edu

Dr. Stein did not indicate any proprietary interest in the subject matter.