Study: Generic PGAs improve adherence in glaucoma patients
SAN FRANCISCO — In the first study to examine the impact of a reduction in glaucoma medication copay on patient adherence, researchers in Michigan have found that switching nonadherent glaucoma patients to generic drugs may be a potential solution to one of the biggest obstacles facing American ophthalmologists in the fight against glaucoma-related blindness - more than half of glaucoma patients do not take their medications as prescribed.
The standard treatment for open-angle glaucoma — the most common form of the disease in the United States — is a class of medications called prostaglandin analogues (PGAs), which are eye drops that lower intraocular pressure. While PGAs are highly effective, the brand name versions are often more costly than other classes of glaucoma drugs, and researchers have suspected that the high cost may be an important reason why so many patients do not take their medication as prescribed. In March 2011, the first and only generic PGA, latanoprost, became available in the United States. At the time, it was priced to save a typical patient approximately $1,300 a year when compared to buying brand name products.
To determine how the generic drug's availability may have impacted adherence, researchers from the University of Michigan Medical School and University of Michigan College of Pharmacy examined claims data from 8,427 glaucoma patients for the 18 months before and after latanoprost became available. All subjects were taking name brand PGAs prior to the availability of generic latanoprost, but after the generic drug's introduction, some stayed on the name-brand medications while others shifted to the generic drug.
The researchers found that while medication adherence improved on average among all patients who were switched to generic latanoprost, those who were on name brand PGAs other than branded latanoprost – such as bimatoprost and travaprost – experienced a greater improvement. Among those who had switched from Bimatoprost, medication adherence rose, on average, from 47% of the time to 61% of the time. Among those who had switched from Travaprost, the average adherence rose from 43% of the time to 54% of the time.
In a subset of patients who had suboptimal adherence prior to the availability of a generic option, the researchers identified several factors associated with an adherence improvement of 25% or more. These included higher prescription copays prior to the introduction of generic latanoprost or lower prescription copays after the introduction of generic latanoprost. The researchers speculate that the lower cost of generic latanoprost may be the primary reason for the improvement. They also found improved adherence among African-American patients who switched to generic drugs, and noted that African-Americans tend to have more severe glaucoma compared to other ethnicities and therefore often have a more complex medication regimen, which affects both cost and adherence.
"Some of my patients require three or four different classes of medications. Individuals' out-of-pocket costs for glaucoma medications can exceed $100 per month, and the high drug cost may deter patients on a tight budget from consistently buying and taking their medications as prescribed," stated Joshua Stein, lead author and associate professor of ophthalmology and visual sciences at the University of Michigan Kellogg Eye Center. "It's reassuring to find that switching patients to more affordable, generic drugs could be an effective solution for a subgroup of patients who have difficulty with adherence."
Stein added that the findings may have applications beyond glaucoma to other chronic conditions – such as high blood pressure, diabetes and high cholesterol – for which patients similarly struggle with medication adherence.
The investigators recommend that ophthalmologists consider switching to generic drugs when available for patients who struggle with adherence. Similarly, they advise patients with glaucoma to talk with their ophthalmologist about whether any of their prescribed medications are available as generic products and if they could be switched to such products when applicable.
The study was published online by Ophthalmology, the journal of the American Academy of Ophthalmology, last week.