Colchicine, a gout remedy so old that the ancient Greeks knew about its effects, used to cost about 25 cents per pill in the US. Then in 2010 its price suddenly jumped 2,000%.

That’s just one of the side effects of a US Food and Drug Administration (FDA) plan to encourage testing of medicines that have been around longer than the modern FDA itself, and so have never gotten formal approval. Companies that do the tests are rewarded with licenses that can temporarily give them monopoly pricing power as most rivals are eased or kicked off the market.

The result-it can bring big paydays for the producers. URL Pharma, the small Philadelphia drugmaker granted rights over colchicine, was bought for $800 million by Takeda Pharmaceutical Co. in 2012. Asia’s biggest drugmaker has since brought in $1.2 billion in revenue from the branded drug, Colcrys, which went on the market at a wholesale price of almost $6 a pill. Takeda says testing for FDA approval made the drug safer.

But patients and hospitals are feeling the pinch, and politicians have begun to notice. Hillary Clinton’s promise to address the issue sent pharmaceutical stocks plunging. Critics say the FDA plan lets entrepreneurs make windfall profits on drugs, where there was never much concern about safety or efficacy.

The program “almost had the opposite effect as intended,” said Joseph Biskupiak, a professor at the University of Utah College of Pharmacy. “The only drugs that got studied are the ones that don’t have a problem,” he added.

The FDA’s rationale is that some drugs have never been measured against modern safety standards, with Michael Levy, deputy director in the compliance office of the FDA’s drug evaluation unit, coining the scheme a success. The agency acknowledges that approving branded versions of old generic drugs may make them more expensive when a sole manufacturer remains to make a medication, but says that’s outside its remit. “FDA does not regulate according to economic factors, nor do we have control over drug pricing,” spokesman Christopher Kelly said.

However, the FDA program, launched in 2006, is only one reason behind the price rise. Others include mergers that reduced competition, and a business strategy by some drugmakers of acquiring niche medicines and raising prices sharply, even without any rebranding.

A survey of more than 21,000 generic drugs by DRX, a unit of Connecture Inc. that tracks drug prices, found the prices of more than 3,500 drugs have doubled since late 2007, ranging from basic chemotherapy medicines to old antibiotics.

Investors who bet on the industry have benefited from the sales increases. Since the end of 2009, a Bloomberg Intelligence index of specialtygeneric drugmakers has almost quadrupled, gaining about four times as much as the S&P 500 Index.

Another drug to jump in price is vasopressin, a bloodvessel constricting agent used in emergencies. To combat the problem, Tenet Healthcare Corp., the fourth-largest operator in US, says it’s started refrigerating vasopressin because that can increase its shelf-life to two years from less than 12 months, so it doesn’t have to replace the drug as often.

