Retail prescription drug spending can be affected by (1) changes in the mix of available drugs, (2) changes in the price of drugs, and (3) changes in the volume of drugs used. The rapid increase in retail drug spending in 2014 and 2015 was driven largely by the introduction of new high-cost drugs, price increases for existing drugs, and the diminishing impact of generic substitution, as fewer brand-name drugs lost patent protection than in previous years. Implementation of the Patient Protection and Affordable Care Act (ACA; P.L. 111-148, as amended) also helped to propel drug demand.14 The rate of prescription drug spending slowed in 2016, even though overall utilization rose during that year, due to factors that included fewer new drug approvals than in previous years, less use of high-cost hepatitis C drugs, and a deceleration in spending for drugs to treat diabetes
