How Do Copayment Coupons Affect Branded Drug Prices and Quantities Purchased?

We estimate the causal effects of drug copayment coupons, which reduce consumer cost-sharing for branded prescription drugs, on net-of-rebate price and quantities sold. Focusing on drugs without generic substitutes, we show that coupon introductions increase quantity sold by 23-25% for the commercial segment relative to Medicare Advantage, where coupons are banned. To quantify the resulting equilibrium price effects, we estimate a discrete choice model of demand for multiple sclerosis drugs and simulate a model of drug price negotiations. We estimate that net-of-rebate prices are 8% higher due to the availability of coupons for most of these drugs.