Mylan lost a major celebrity spokeswoman Thursday as actress Sarah Jessica Parker slammed the company over its drastic price hikes of EpiPen.

Parker said on Instagram Thursday that she was "disappointed, saddened and deeply concerned by Mylan's actions." The company has raised the price of the allergy treatment by 400 percent since acquiring it in 2007, with some doses costing up to $500.

The "Sex and the City" star took part in an ad campaign funded by Mylan to raise awareness about anaphylaxis, a life-threatening allergic reaction that EpiPen is supposed to treat.

On the campaign's website, Parker recounts that her son has allergies to peanuts and hazelnuts, allergies that were discovered when he went into anaphylactic shock.

"It's amazing to me how drastically the dialogue around food allergies has increased over the past decade," she wrote on the website anaphylaxis101. "However, like any major health concern, there is still much more we can do to help the millions of people who are at risk for anaphylaxis to understand just how severe allergies can be."

Parker's tone shifted significantly on Thursday, when she said she recently learned of the increase.

"I do not condone this decision and I have ended my relationship with Mylan as a direct result of it," she wrote.

In response to the public backlash, Mylan announced Thursday it would offer a $300 discount card and expand public assistance for underinsured and uninsured to get the drug.

However, that did little to mollify angry lawmakers.

"This step seems like a PR fix more than a real remedy, masking an exorbitant and callous price hike," said Sen. Richard Blumenthal, D-Conn.