The US spent 13% more on prescription medications in 2014 than it did the year earlier, pharmacy benefits manager Express Scripts reported in its annual drug trend report.

Unsurprisingly, new hepatitis-C medications, including Gilead Sciences’ medications Sovaldi (sofosbuvir) and Harvoni (ledipasvir/sofosbuvir), were cited as major drivers, as was Johnson & Johnson’s HCV drug Olysio (simeprevir).

The PBM noted that the spending increase for hepatitis-C drugs was so great that it pushed medications for this condition into the top 10 specialty drug classes of 2014. Hepatitis-C medications did not even make it into 2013’s top 10 specialty drug list, but last year it was fourth, behind specialty medications for cancer, multiple sclerosis and inflammatory conditions.

Although specialty medications accounted for more than 31% of last year’s US drug spend, Express Scripts expects things will slow down to what it called a sustainable rate of increase of around 22% over the next three years, even if the conditions the drugs treat may not be thought of as requiring specialty treatments.

As an example, Express Scripts said that cholesterol-fighting PCSK9s will end up on the specialty medications list once they are approved by the FDA. Express Scripts explained that although these medications are initially expected to be used by a small band of patients with high cholesterol, spending will increase when and if these drugs are prescribed for patients that cannot tolerate statins, regardless of whether they are patients with extremely high cholesterol levels. This broader use would somewhat mitigate the potential impact that patent expiries of medications like AstraZeneca’s Crestor (expiring in 2016) and Merck’s Zetia (2017) and Vytorin (2017) can have on spending.

Setting specialty medications aside, Express Scripts said that 2014 showed just how much the pharmaceutical industry has altered its focus from developing drugs that treat common conditions to ones that offer smaller patient populations medications with higher price tags. The company expects more manufacturers to attach high prices to drugs for “non-orphan conditions like hepatitis C.” Merck’s Keytruda, a cancer treatment appropriate for specific genetic profiles, was among the medications noted as part of the high-price cohort of drugs that treat small patient populations.

Generics are also expected to provide less of a savings going forward. The PBM noted that whereas prices for generics fell 20% between 2013 and 2014, prices fell 30% between 2012 and 2013. And, as noted by Congress, Express Scripts said prices for some generics have actually increased.

Spending on diabetes medications—which were the most expensive traditional medications for the fourth year in a row—also shows how resilient brands can be, even with cheaper options available. Express Scripts said generics accounted for fewer than half of 2014’s diabetes medications, even though the most common treatments, which include metformin and glimepiride, “are generic drugs with branded formulation patents that expired at least a decade ago.”

Express Scripts anticipates that diabetes-medication spending will rise by just over 18% every year for the next three years. That increase will occur because of higher prices related to brand innovation and because patients will likely switch from generic monotherapies to new combination products.

The PBM does expect pricing on some medications to fall between now and 2017 and said “stagnant utilization” of high-blood-pressure medications and the use of generics will drive down spending for these drugs. They also noted that this is a bit of a catch-up because generic Diovan, a high-blood-pressure medication, only just hit the market last June, after legal problems delayed manufacturing. Express Scripts also expects over-the-counter and generic versions of heartburn drugs will lower spending for those medications, among others.