Pharmacy benefit manager (PBM) Express Scripts reported that, in 2017, it had a record low year-over-year change in per-member drug spending across commercial, Medicare, Medicaid, and health insurance exchange plans.

Among commercial plans covering employees and their families, said Express Scripts, drug spending increased by just 1.5% per person, down from 3.8% in 2016. Calling this rate a “historic low,” the PBM said in a statement that this level of spending growth is the lowest that it has measured since 1993.

Per-member spending increased by larger margins for Medicare and Medicaid, which rose by 2.3% and 3.7%, respectively, but health exchange plans saw a 3.3% drop in drug spending, which Express Scripts says was driven by lower unit cost trends for pain and inflammation drugs, as well as for cholesterol drugs and neurological disorder therapies.

Express Scripts credits a reduction in unit costs of traditional drugs and increasing generic fill rates for driving down total spending. Spending on specialty drugs—which accounts for 40.8% of drug spending—was influenced by the availability of generic versions of such high-cost therapies as Copaxone (glatiramer acetate injection). Specialty drug spending was up 11.3% last year, however.

Inflammatory diseases continued to lead all classes in spending in both commercial plans and health insurance exchange plans, while diabetes and HIV led per-person spending in Medicare and Medicaid plans, respectively.

Notable decreases in spending were observed over the year; among commercial plans, hepatitis C drug utilization dropped by over 40%, leading to a 31.2% decrease in per-member spending. Medicaid and health insurance exchange plans also spent less per member per year on hepatitis C treatments, with drops of over 27% and 35%, respectively. Among Medicare plans, per-member spending decreased by more than 25% for drugs used to control high blood cholesterol.

In looking to the years to come, Express Scripts says that costs will continue to rise for the treatment of inflammatory diseases, “as biosimilar savings are not expected until after 2020.” The PBM expects to see a 16% rise in spending on inflammatory conditions in 2018, followed by a 15% rise in 2019, and a 14% rise in 2020.

The Express Scripts report is similar to that of fellow PBM Prime Therapeutics, which said that, in 2017, its per-member-per-month drug spending trends were down by 0.2% among commercial plans, 0.8% among Medicare Part D plans, and 5.4% for Medicaid.

However, cautioned David Lassen, PharmD, chief clinical officer at Prime, “Low trend is not synonymous with low cost.” He added, “Prescription drugs still represent [20% to 30%] of costs for our health plans and employers.”