WASHINGTON — The Food and Drug Administration is taking steps to boost the number of generic prescription drugs in an effort to make medicines more affordable and to prevent price gouging.

Copycat pills normally are much cheaper than original brand-name drugs. But in some cases, when a generic has no competition, companies have drastically increased prices.

New commissioner Dr. Scott Gottlieb said Tuesday that the FDA will now give priority reviews to new generic drugs until there are at least three on the market.

That’s the level at which prices tend to drop sharply, up to 85 percent off the brand-name price.

The agency also published its first list of brand-name drugs that no longer have a patent’s protection but don’t yet have generic competition.