An aging population is not the only cause of headache for policymakers trying to keep the nation's medical costs down — now they have "superexpensive" drugs to deal with.

Medical expenses paid to hospitals and clinics across the nation were estimated to have reached a record ¥41.46 trillion in fiscal 2015, up 3.8 percent from the previous year, the Health, Labor and Welfare Ministry announced Tuesday. The figure marks a ¥1.5 trillion rise from fiscal 2014.

Of the total, costs of prescription drugs stood at ¥7.9 trillion, up ¥680 billion, or 9.4 percent, from the year before. In particular, antiviral drugs — including the hepatitis C drug Harvoni, which was approved for use under the public insurance program last year — alone accounted for ¥414 billion, marking a 250 percent increase from the year before, according to the ministry.