“Generic drugs were meant to help make medications affordable for the millions of Americans who rely on prescriptions to manage their health needs,” Senator Sanders said in a statement. “We’ve got to get to the bottom of these enormous price increases.”

Some of the rises have been huge, according to data released by the lawmakers. The price that hospitals and pharmacies pay for a bottle of 500 tablets of doxycycline, a decades-old antibiotic, rose to $1,849 in April, from $20 in October 2013. The price they pay for a bottle of pravastatin, a drug to lower cholesterol, rose to $196 from $27 in that same time. The price of a pill of digoxin, a centuries-old medicine that is irreplaceable for some cardiac patients, rose to $1.10 this summer from 11 cents in 2012.

Some or all of such price increases are passed on to patients.

Late last week, the lawmakers sent letters to 14 drug makers that make or distribute the 10 generic drugs, requesting explanations for price increases. They may hold hearings depending on the response, which is due by Oct. 23. Some manufacturers have already promised cooperation.

“The first thing we need to understand is why these drug companies are raising their prices so dramatically in such a short period of time, which is why we asked for information about the costs to produce these drugs compared to the prices they are now charging,” Representative Cummings said this week. “Once we receive that information, we will be in a better position to evaluate the root causes of these massive increases and, if necessary, consider reforms.”

In a statement, Ralph G. Neas, president and chief executive of the Generic Pharmaceutical Association, said that facts about generic drug prices had been “mischaracterized,” focusing on a handful of drugs with big price increases, among the thousands of “safe, affordable” generic medicines.