Impact of a prior authorization for pregabalin on health plan drug expenditures

The objective of this study is to examine the financial impact of a prior authorization (PA) intervention for pregabalin in a commercially insured US population via an economic model.

An Excel-based model was developed to simulate 2 hypothetical scenarios for health plans: one with a PA on pregabalin, and another without a PA. In the PA scenario, a variable percentage of pregabalin prescriptions were assumed to be approved and dispensed, the remainder being denied or a substitute product dispensed (branded or generic alternatives). In the "no PA" scenario, all pregabalin prescriptions were assumed to be filled. The market shares of these products, including pregabalin, were based on secondary prescription data. The model calculated the total drug acquisition cost and cost of PA administration in each scenario for a cohort of 1000 patients over a 1-year period. Patients switching to pregabalin following denial were accounted for in the model. Sensitivity analyses were carried out varying the PA approval rates and prescription share of pregabalin and limiting the range of substituted products.

The pregabalin prescribing rate was set to 10.3% in both the PA and "no PA" scenarios, with a denial rate of 50% in the PA scenario, consistent with the IMS prescription volume. The calculated drug acquisition cost for the PA scenario was $885,564 compared with $888,822 for the "no PA" scenario, a difference of 0.4%, after factoring in the cost of PA administration. The calculated PA administration cost was $4121. Eliminating the PA administration cost results in a cost for the PA scenario of $881,443, 0.8% below the "no PA" scenario. Lowering the pregabalin PA approval rate from 50% to 10% decreased the costs of the PA scenario to $879,660, 1.0% lower than the "no PA" scenario. Raising the pregabalin market share to 20% in the "no PA" scenario increased the costs of that scenario to $902,714, 1.9% higher than the PA scenario. Limiting the substituted products for denied pregabalin prescriptions in the PA scenario to the 2 most common products, valproate sodium and gabapentin (both generics), lowered the cost of the PA scenario to $875.412, 1.5% below the "no PA" scenario cost. With half of the denied pregabalin patients switching to pregabalin during the course of the year, the cost of the PA scenario increased to $892,550, 0.4% higher than the "no PA" scenario.

Potential savings due to PA protocols on pregabalin are low, in the 1% to 2% range across a variety of scenarios, because of the relatively low pregabalin market share (about 10%) in typical health plans and the absence of a significant difference in cost for the most commonly substituted products. Patients who switch to pregabalin after an initial denial will further reduce savings to health plans.