Mylan must still answer questions on EpiPen, Sen. Grassley says

There needs to be more transparency in drug pricing — including looking at the middlemen — but when it comes to the controversy about Mylan's pricing of its EpiPen, the company still has a lot of questions to answer, Sen. Charles "Chuck" Grassley, R-Iowa, said Thursday.

"Transparency and things of that nature I think are very, very important but in this particular instance we've got one company with a monopoly on the product going up more than 400 percent," the chairman of the Senate Judiciary Committee said in an interview with CNBC's "Power Lunch."

The drug, used to counteract a potentially fatal allergic reaction, has a retail cost of more than $600. On Thursday, the company announced it increased rebates to many consumers.

Mylan CEO Heather Bresch told CNBC on Thursday that she too was "frustrated" over the EpiPen furor, noting that the price reflects a system where the drug goes through middlemen before it gets to patients.

She also said she has reached out to Grassley to talk about the issue, in response to a letter the senator sent on Monday requesting information about the sharp price increases.

Grassley said that someone from the company called his office, but he said he wanted to get all of the questions he posed in his letter answered before having a meeting.

"I'm going to wait until then and read on paper their justification for these … gigantic increases that they've had that I think are unjustified."

The senator also sent a letter this week to the Food and Drug Administration, asking for information about its approval process and other steps for alternatives to the EpiPen.

"Competition will draw down the price and we want to know whether that process can be speeded up to get competition to the market," he told CNBC. "I think one of the reasons Mylan had the guts to move this price up so rapidly is because they do have a monopoly, and about 40 percent of their clientele is Medicaid, so they can cheat the taxpayers as much as they're cheating the individual families."

Sen. Amy Klobuchar, D-Minn., has also called for Mylan to explain its price hikes. She told CNBC on Thursday that she has spoken to Bresch and that the two will meet.

She also said she appreciated that the company has done something to ease the burden on consumers.

However, "I don't think that fixes a systemic problem we're seeing across pharmaceuticals where the top 10 drugs in America, four of them have had over 100 percent increases in just the last four years," she said in an interview with "Closing Bell."

Klobuchar, whose daughter has a severe nut allergy and carries the EpiPen, has also called for the Federal Trade Commission to investigate Mylan for possible antitrust violations.

She said also she has a bill pending with Sen. John McCain, R-Ariz., that would allow cheaper, safer drugs into the U.S. from Canada to create competition.

"My wish is that there would be a generic alternative, a competitor" to the EpiPen, Klobuchar said.

— CNBC's Dan Mangan contributed to this report.