WOONSOCKET, R.I. — A CVS Caremark Corp.-sponsored study found that patients who face co-pays of $50 are almost four times more likely to abandon prescriptions at a pharmacy than those paying $10.

Besides determining that a direct correlation exists between the amount of a patient’s out-of-pocket co-pay and the likely abandonment of a prescription, the study — done in tandem with Harvard, Brigham and Women’s Hospital — found that electronic prescriptions are 65% more likely to be left abandoned at a retail pharmacy by patients than handwritten prescriptions.

Published in the Annals of Internal Medicine, the study is said to be the first analysis to systematically evaluate rates and predictors of prescriptions abandoned at the pharmacy.

“This research gives us new insight into an area of nonadherence that we did not have before and shows we have opportunities to change patient behavior,” states Larry Merlo, president and chief operating officer of CVS Caremark. “We need to be more attentive to reasons why patients may be abandoning prescriptions and work to help them stay on their medications.

“We continue to be a strong proponent of e-prescribing because we recognize the benefits it can provide, such as improving the accuracy and quality of prescription delivery and reducing paperwork to make pharmacy care more efficient.”

Researchers reviewed all prescriptions dispensed at CVS/pharmacy locations between July 1 and September 30, 2008. Of prescriptions that were abandoned, more than half were never filled at any pharmacy, while some were filled at other pharmacies at a later date. The team concluded that the pharmacy industry would benefit from learning more about prescription abandonment.

Researchers reported that the higher rate of abandonment for e-prescriptions appears to occur because patients with written prescriptions must physically bring the request for medications to the pharmacy, whereas patients with e-prescriptions are not required to take any step to begin the prescription filling process.

Also, the rate of e-prescription abandonment appears high because pharmacies can track them as abandoned, unlike with paper prescriptions never actually brought to a pharmacy.