A report released on Tuesday showed a jump of 13% to $374 billion in 2014 in US spending on prescription medicines. The leap is the biggest since 2001, and is attributable to surge in demand for expensive new breakthrough hepatitis C treatments.

The contribution to the double-digit spending rise in 2014 also came from demand for newer cancer and multiple sclerosis treatments, hike in prices of branded medicines, particularly insulin products for diabetes, and introduction of few new generic versions of big-selling drugs.

"We certainly expect to see growth in the market size and spending level in 2015, but not at the rate of growth that we're reporting for 2014. We know that the patent expiry impact will be larger in 2015 than it was last", said Murray Aitken, executive director of the IMS Institute for Healthcare Informatics, which compiled the report.

More than 161,000 patients went for new hepatitis C treatments from Gilead Sciences Inc in 2014. The treatment has been seen as the best cure for the liver-destroying virus, with few side effects.

Sales of Sovaldi helped Gilead generate a record-breaking $10.3 billion in first year alone. The report also highlighted the large number of so-called orphan drugs that were launched the market in 2014. As many as 18 expensive medicines were introduced in 2014 for rare diseases.

The entry of new generic versions of branded drugs resulted in spending reduction by only about $12 billion in 2014. It was lesser than about $20 billion the year before and $29 billion in savings in 2012.

The US Food and Drug Administration's sanctions against India's Ranbaxy caused delays for cheap versions of AstraZeneca Plc's blockbuster heartburn drug Nexium, which also contributed in the lesser savings from generic drugs in 2014.