Strategies such as preventive drug lists with $0 copays for generics, as well as formulary strategies that promote the use of generics first, the report said, helped reduce costs for high-utilization categories such as antihypertensives and cholesterol-reducing drugs. Also, plan designs pushing lower-cost options and targeted adherence interventions helped to drive that higher compliance rate among patients who kept taking medications.

Member out-of-pocket cost, per member per month, declined slightly from 2016's $11.99 to $11.89 in 2017, while three out of four members spent under $100 for their prescriptions. Nearly 90 percent of members, it adds, spent less than $300.

Members with chronic conditions stuck to medications better, with utilization up by 1.7 percent; that meant the overall growth in drug prices was up per member per year for 2017 by 1.9 percent. And while manufacturer-driven price inflation for specialty drugs was 8.3 percent in 2017, the use of formulary strategies, indication- and outcomes-based contracting and cost-cap based rebates, restricted that increase to 3.7 percent for clients.

The generic dispensing rate for CVS Health PBM clients was above 86 percent, the report adds, with the number of optimally adherent members with chronic conditions such as diabetes, high blood pressure and high cholesterol increasing by as much as 1.8 percentage points.

In addition, late in the year CVS Health introduced a means for prescribers to see in real time member-specific out-of-pocket costs of a prescribed medication, as well as the costs of clinically appropriate alternatives. That allows the prescriber to make more informed decisions and offer members medication options that may be more affordable.