Prescription drug spending rose 9% to $324 billion in 2015, compared to 2014, in part due to high-priced hepatitis-C drugs like Gilead Sciences’ Harvoni, the Centers for Medicare and Medicaid Services said.

The rate of drug spending did moderate last year, however, increasing by 9% compared to 2014’s spending growth rate of 12.4%. Still, prescription drug spending grew faster than any other healthcare service in 2015 tracked by the CMS.

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That rise in drug spending was attributed to high-priced hepatitis C drugs, with Gilead Sciences’ Harvoni leading the charge, a CMS official said on a call. Another Gilead HCV drug, Sovaldi, was named as a driver in drug spending in 2014. Sovaldi received FDA approval in late 2013; Harvoni was approved the following year. The list prices for the drugs are $84,000 and $94,500, respectively. The report said other drivers were increased spending on new medicines, price hikes for existing branded drugs, and higher spending on generics.

Overall healthcare spending grew by 5.8% to $3.2 trillion in 2015, the largest increase in eight years, but similar to the 5.3% growth rate seen in 2014. Health spending accounted for 17.8% of the GDP in 2015, compared to 17.4% in 2014.

More people have health insurance as a result of health coverage expansions under the Affordable Care Act. The CMS analysis said that private health insurance spending rose by 7.2% in 2015, up from 5.8% in the year prior.  

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“While the 2014 and 2015 increases occurred more than five years after the nation’s last recession ended, they coincided with 9.7 million individuals gaining private health insurance coverage and 10.3 million more people enrolling in Medicaid coverage,” Anne Martin, an economist in the CMS Office of the Actuary said in a statement. “An additional contributing factor is the rapid growth in retail prescription drug spending.”

The ongoing utilization of costly new HCV treatments may continue to raise overall spending, according to recent government reports. The Centers for Disease Control and Prevention reported in May that acute cases of HCV doubled from 2010 to 2014. Virginia’s health commissioner said this week that the state has seen a sharp rise in hepatitis-C cases, with 6,600 reported in 2014 and more than 8,000 reported in 2015, due to the opioid abuse epidemic, according to the AP.