Think your medications are really expensive? They are. Antiviral drugs used to treat HIV and hepatitis C virus (HCV) remain the most expensive medications vis-a-vis Medicaid spending, according to a new analysis by the Kaiser Family Foundation.

The study, which examined Medicaid outpatient prescription drug spending between 2014 and 2017 found that, overall, rebates are increasing and spending is on the rise. Utilization of the program has also increased ,from 621.7 million prescriptions in 2014 to 752.9 million in 2017—an overall uptick of 21 percent.

Eight of the 10 most expensive prescriptions remained in the top 10 of Medicaid spending, but their positions on the list shifted. However, HIV and hepatitis C consistently ranked at the top of the list, accounting for nearly 14 percent of total outpatient drug spending for the program. Hepatitis C drugs alone cost nearly $3.2 billion between 2014 and 2017, despite being prescribed the least.

Currently, Medicaid covers more than 280,000 people living with HIV—about 40 percent of all those living with HIV in the United States. Study authors also wrote, “Of the up to 5 million people in the U.S. with hepatitis C, a disproportionate number are enrolled in Medicaid.”

Other highly utilized drugs on the list included diabetes treatments, opioids, asthma and chronic obstructive pulmonary disease medications, anticonvulsants, narcotic and non-narcotic painkillers, blood pressure medications, ulcer drugs, antihistamines and dermatological treatments.

Researchers said they expect Medicaid spending to surge in the coming years and that action must be taken on the state and federal levels to address concerns over high-cost medications, notably those used to treat HIV and hepatitis C.