stat tracker
A Second Medication May Reduce Glaucoma Patients' Compliance

lan L. Robin, M.D., David Covert and colleagues conducted a study to examine the effect of adding complexity to a glaucoma medical treatment regimen — specifically, what would occur to the refill rate (and, by inference, to compliance) when a second medication was added to a currently used once-daily drug.

The authors note that, treatment compliance seems to be at best 75% in most studies. Even in symptomatic diseases where lapses in therapy may result in clinically significant symptoms (e.g., epilepsy), it is still a problem. In glaucoma, the lack of overt symptoms, in theory, would tend to decrease the adherence of the patient to pharmacotherapy requiring frequent self-treatment.

Participants

Dr. Robin's study compares medication refill rates for two groups of glaucoma patients. The participants included patients of a large national healthcare provider who had received a prescription for latanoprost between July 1, 2001 and June 30, 2002. One group was composed of 1,784 patients who had a second medication added and the other group had 3,146 patients who remained on monotherapy.

Methods

For each patient, the mean number of days between refills was calculated for both the period before, and that subsequent, to the addition of the second medication, and an interperiod difference in refill interval between the two periods was calculated.

Results

A decrease in adherence associated with the addition of another therapy, irrespective of the size, frequency of administration, or type of adjunctive medication was found. A categorical analysis was performed on the refill intervals after the addition of the second-line drug. In approximately one third of patients (33.7%), when a second drug was added the refill interval for latanoprost was the same or less (i.e., earlier) than with the prior monotherapy. An additional 43.3% refilled their latanoprost within 2 weeks of the prior monotherapy experience. However, for an additional 22.9%, the interval was increased by 2 weeks. A similar distribution of refill intervals was seen when stratified by fill size or second-line drug.

Conclusions

Treatment adherence is a critical factor in the success of glaucoma therapy. The addition of a second medication and an increase in the complexity of glaucoma therapy was associated with a statistically significant increase in the interval until refill, or a presumed decrease in adherence. This increase was clinically significant, as approximately one fourth of patients increased the time between refills by almost 2 weeks.

This increase in refill intervals may affect IOP control. It is suggested that, when adding a second drug, physicians need to consider the possible impact on the patient's adherence to the first drug.

About these data: This study first appeared in Ophthalmology 2005;112:863–86 and was sponsored by Alcon Laboratories, Inc., Fort Worth, Texas. Dr. Robin is a consultant to, and Mr. Covert is an employee of and stockholder in, Alcon Laboratories, Inc. Dr. Robin is an associate professor at both the Johns Hopkins University Schools of Medicine and Public Health. In addition, Dr. Robin is also a consultant to Pfizer and Merck. Correspond to Alan L. Robin, M.D. at 6115 Falls Road, Suite 333, Baltimore, Md., 21209. E-mail: glaucomaexpert@cs.com.