Anticonvulsant use after formulary status change for brand-name second-generation anticonvulsants

Anticonvulsant medications are commonly used for off-label indications. However, managed care organizations can restrict utilization of medication to indicated uses only.

To evaluate the pattern of off-label use of second-generation anticonvulsants after implementing a formulary change.

We did a retrospective analysis of an administrative pharmacy claims database for a managed care plan with more than 1 million members continuously enrolled during 2004-2005. The study evaluated off-label use and explored pharmacy utilization patterns (by physician specialty, region, plan type, age, sex, copayment) across the study population following the formulary change.

A total of 10,185 patients had at least 1 pharmacy claim (total of 137,638 claims) for a second-generation anticonvulsant during the study period. Most members were female (68%), and 4.9% were <18 years old. A total of 3986 of 4698 patients (84.8%) and 4600 of 5487 patients (83.8%) had anticonvulsants prescribed for off-label use in 2004 and 2005, respectively (P = .162). The off-label usage pattern varied for individual anticonvulsants in 2004 and 2005 (P <.050), which may have been because of the change to nonpreferred coverage. Primary care physicians accounted for 41.3% of the prescribing of second-generation anticonvulsants for off-label uses, followed by neurologists (9.4%), psychiatrists (2.8%), and other (46.5%). The coverage change resulted in cost savings for the plan of $0.16 per member per month.

The off-label usage pattern varied for individual anticonvulsants in 2004 and 2005. Future considerations for controlling off-label use may include requiring prior authorization and provider education.