Mylan NV turned down a U.S. senator's request to testify this month at a congressional hearing on the price of its allergy shot EpiPen, after two government agencies also invited said they won't attend.

Senate Judiciary Chairman Charles Grassley (R., Iowa) has scheduled a Nov. 30 session to examine how the drugmaker gave Medicaid smaller-than-legally-required discounts on EpiPen, potentially denying the government millions of dollars. The U.S. Department of Justice has reached a $465 million settlement with Mylan, which Grassley and other lawmakers say isn't enough. Details of the settlement haven't been released by the United States or Mylan.

The Justice Department and the Centers for Medicare and Medicaid Services, which oversees Medicaid, have declined to testify. With Mylan declining as well, Grassley could compel their presence with a subpoena, Jill Gerber, a spokeswoman for the senator, said in an email.

"The Obama administration is dodging accountability for an expensive problem, and now a company is following its bad example," Grassley said in a statement. "It's a shame government agencies and the company are ducking accountability under a voluntary process. One way or another, I intend to get answers for patients and taxpayers."

Mylan's lawyers at Latham & Watkins LLP wrote Grassley on Friday to inform him the company wouldn't testify.

"Given the stated focus of the proposed hearing, the fact that it involves a pending matter, and that the government agencies in question will not be able to send a witness to testify or provide further information, Mylan respectfully declines," the law firm said in the letter, which was released Monday.

Grassley said this month that Medicaid was informed in 2009 by the Department of Health and Human Services' inspector general that the company should have been giving larger rebates on the allergy shot.

Grassley also on Monday asked the Securities and Exchange Commission if it is looking into whether Mylan misled investors when it announced the settlement with the Justice Department, since the government hasn't confirmed details of the settlement. Mylan said last month that the SEC had asked it to turn over documents related to the Medicaid payments.