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.