The Food and Drug Administration has left hundreds of millions of dollars from drug makers in the bank, with experts questioning whether the regulatory agency could do more to speed up product reviews and increase competition.

The research firm Avalere Health issued a report that found the FDA has received $7.67 billion in user fees from drug makers since the program started in 1992. However, it has $300 million in unspent fees from prescription and generic drugs, the report said.

"The significant unspent funds left over from user fee programs suggest that FDA could do more to accelerate product reviews," said Jay Jackson, a manager at Avalere. "Particularly with public concern around drug prices, speeding approval of the second-to-market products can increase competition that may result in lower net prices."

The FDA usually has carryover balances each year, and the unspent funds from the year before affect the rates drug and device makers are charged.

A generic or brand name drug maker must pay the FDA to apply for a new drug application. This year, the fee was $2.3 million for any prescription drug application that included clinical trial data.

In addition to user fee programs for drugs, the agency has programs for devices and for biologic drugs, which are treatments that are derived from human tissue. All of the FDA's user fee programs will expire in September 2017, and the agency must ask Congress to reauthorize them.