CHICAGO – After calling for a routine prescription refill, Craig Elliott got a rude shock: His bill was going up fivefold.

The 44-year-old piano tuner and guitar instructor, who has health insurance, used to pay $20 for a three-month supply of his generic epilepsy drug as a member of Walgreens' Prescription Savings Club. But recently, the price shot up to more than $100, forcing him to order month by month.

"I'll get by … [but] I don't like now having a larger bill every month," Elliott said.

Countless other Americans are feeling the same sticker shock at the drugstore. Historically costing pennies on the dollar compared with a brand-name drug, generic drugs have long been considered a vital weapon in the fight to contain soaring health care costs. But in the past year, the price of many generics is disconcertingly moving in the wrong direction, drawing the attention of Congress and pinching the wallets of consumers as well as pharmacies and insurers.

"We are talking about the need of the American people to be able to afford the medicine that their doctors prescribe," U.S. Sen. Bernie Sanders, I-Vt., chairman of a Senate health care subcommittee, said at a hearing on the issue on late last week. "There appears to be now a trend in the industry where a number of drugs are going up at extraordinary rates. We wanted to know if there was a rational economic reason as to why patients saw these price increases or whether it was simply a question of greed."

Experts say raw material shortages, consolidation in the industry and medical advancements that make replicating brand-name drugs more expensive have all contributed to skyrocketing costs.

Craig Elliott’s medical bills have soared since his epilepsy drug rose from $20 to $100.

According to Catamaran, a pharmacy benefit manager that administers prescription drug programs, consumers and insurers paid an average of $41.88 for a generic drug prescription in recent years, up from a four-year average of $14.21 between 2005 and 2009. Today, more than a third of available generics cost insurers and consumers more than $100 per prescription, company data show.

"People who don't have insurance, they're picking up the full fare of these drugs," said Catamaran's chief medical officer, Dr. Sumit Dutta. "And they're often not in the best place to handle the cost of these medications."

A Pembroke Consulting analysis of federal data shows that the price pharmacies pay for generics over the past year has soared, too, by as much as 17,700 percent. One in 11 generic drugs have more than doubled in acquisition cost for pharmacies over the past year.

To cope, insurance companies have introduced co-payment tiers to their plans to offset rising generic prices, Dutta said.

Rising prices, but why

Walgreen Co., which cited the skyrocketing generic drug prices as an obstacle for 2015 profits, has a similar tiered system with its Prescription Savings program, a membership plan that offers discounts on services and drugs. The generic epilepsy drug that Elliott takes, Carbamazepine, had previously been on its list of value-priced generics but was removed when the price increased, a Walgreen spokesman said. According to Pembroke Consulting, the average pharmacy acquisition cost of that drug increased about 22 percent between July 2013 to July 2014.

A spokeswoman for Teva Pharmaceuticals, one of six manufactures of the epilepsy drug according to the U.S. Food and Drug Administration website, declined to say why the price of Carbamazepine has been rising.

"Teva is committed to ensuring access and providing high-quality, affordable medicines to U.S. patients," the spokeswoman said in an e-mailed response. "While it is possible to find examples of generic medicines that have increased in price, these select instances are not indicative of the overall market trend."

The largest price increase from 2013 to 2014 was a 500 milligram capsule of Tetracycline, an antibiotic used to treat bacterial infections. That dose went up in price 17,714 percent, from 5 cents per pill to $8.59. An FDA spokeswoman said a more than two-year shortage due to unavailability of raw materials to make the drug, as well as manufacturing issues, was resolved in March.

The rising prices have caught the attention of Congress, and in October Sanders and Maryland's Rep. Elijah Cummings requested financial documents from 14 pharmaceutical companies across the country.

Last year, CVS Caremark announced a partnership with Cardinal Health, giving it more generic drug buying power. Walgreen Co. works with AmerisourceBergen and Alliance Boots and McKesson announced its acquisition of Celesio in January. Those three groups wield a huge amount of purchasing power, which should keep generic drug prices down.

"What the American people are entitled to know," Sanders said, "is why there are a number of generic drugs that have seen a huge increase in prices in recent years."